Disk media, and method of and device for recording and playing back information on or from a disk media

ABSTRACT

In a video disk recording/playback device for converting a digital video signal or the like into high-efficiency coded data and recording the coded data on a video disk, or for restoring high-efficiency coded data recorded on the video disk and reproducing an output image, wherein said digital video signal is composed of a succession of video signals of a plurality of frames and including an I picture encoded within a frame, a P picture interframe coded by forward motion compensation with reference to said I picture and/or another P picture, and a B picture interframe coded by motion compensation in both directions with reference to said I and/or P pictures temporally preceding and succeeding the B picture, there are further provided a means for recording in an image information table set up on said video disk all of the start addresses of coded data representing selected images such as images to be retrieved and the start addresses of data containing information required for reproducing the coded data. With the above configuration, retrieval of all kinds of images of I, P, and B pictures is possible by recording all of the start addresses of coded data representing selected images such as images to be retrieved and the start addresses of data containing information required for reproducing the coded data in the image information table on the video disk.

This application is a continuation of application Ser. No. 08/539,339filed on Oct. 4, 1995, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a disk media, such as a video disk oroptical disk for recording a digital image signal, such as an imagesignal having been coded, e.g., converted to high-efficiency coded data,and a method of and device for recording and playing back a digitalimage signal on or from such a disk media.

a high-efficiency-coded data on a video disk, and method and device forplaying back the image by restoring the high-efficiency-coded data fromthe video disk.

The present invention also relates to a method of performing fastplayback or retrieval from a disk media.

FIG. 40 shows a conventional optical disk recording/playback devicedescribed in Japanese Patent Kokai Publication No. 114369/1992. Asillustrated, it comprises an A/D converter 12 for converting a videosignal, audio signal, or the like into digital information, aninformation compressing means 13, a frame-sector conversion means 14 forconverting compressed information into sector information whose lengthis equal to an integer multiple of a frame, an encoder 15, and amodulator 16 for conversion into modulated codes so as to reduceinter-code interference on a recording media. A laser drive circuit 17and a laser output switch 18 serve to modulate a laser beam according tothe modulated codes.

An optical head 19 is for emitting the laser light. An actuator 20 isfor tracking the light beam emitted from the optical head 19. A traversemotor 21 is for moving the optical head 19. A disk motor 22 is forrotating a disk 23.

Reference numeral 24 denotes a motor drive circuit, 25 denotes a firstcontrol circuit, and 26 denotes a second control circuit. A playbackamplifier 27 is for amplifying a playback signal sent from the opticalhead 19. A demodulator 28 is for acquiring data from a modulated signalthat has been recorded. Reference numeral 29 denotes a decoder, and 30denotes a frame-sector inverse conversion circuit. An informationexpanding means 31 is for expanding compressed information. A D/Aconverter 51 is for converting expanded information into, for example,an analog video signal or audio signal.

FIG. 41 is a simplified illustration of a data structure (layeredstructure) according to the moving picture experts group (hereinafterMPEG) system that is becoming the standard for transmission and storageof digital moving picture information in compressed form.

In FIG. 41, reference numeral 51 denotes a sequence formed of aplurality of image information blocks, also called GOPs (groups ofpictures) 52 and sequence headers. Each GOP 52 is formed of a pluralityof pictures (screens) or image data for a plurality of frames 53. Eachpicture (screen) is divided into slices 54, and each of the slices 54 isformed of a plurality of macroblocks 55. Each macroblock 55 is formed offour adjoining blocks 56y of luminance signal (Y), one block 56b of acolor difference signal (Cr), and one block 56r of another colordifference signal (Cb). The positions of the blocks 56b and 56r of thecolor difference signals are associated with the positions of the fourblocks 56y of the luminance signal.

One block 56y of luminance signal is formed of eight pixels by eightpixels, and forms a minimum coding unit.

The block 56y, 56b, 56r is regarded as a unit for informationcompression based on discrete cosine transform (hereinafter DCT). Themacroblock 55 is a minimum unit for motion-compensated prediction.Detection of a motion vector used for the motion-compensated predictionis carried out taking in macroblock units, with regard to eachmacroblock.

The coded data is output as a bit stream (continuous serial data) havinga structure described above.

The sequence 51 has a structure shown in FIG. 42. In the figure, 65a,65b, 65c and 65d denote GOPs, and 66a, 66b and 66d denote sequenceheaders (SHs). The sequence headers are provided to designate the imageformat such as the number of pixels, the number of lines of the image,and may be appended to the head of all or only some of the GOPs. In thefigure, GOP1, GOP2 and GOP4 are provided with a sequence header appendedto the head thereof, while GOP3 is not provided with a sequence header.Provided at the start of the GOP is data (hereinafter referred to as"time code") indicating the time from the start of the sequence (title,program).

FIG. 43 shows a coding scheme for a case where one GOP 52 is composed often pictures (screens, frames). In FIG. 43, reference numeral 67 denotesan I picture that is image information subjected to informationcompression based on intra-frame DCT. 68 denotes a P picture that isimage information subjected to the information compression based onintra-frame DCT as well as to motion compensation using the temporallypreceding I picture 67 as a reference screen. 69 denotes a B picturesubjected to the information compression based on intra-frame DCT and tomotion compensation using the temporally preceding and succeeding Iand/or another P pictures 67, 68 as reference screens.

Next, the operations of the conventional optical disk recording/playbackdevice will be described. With the advancement of compression of digitalimage information technology, it has become possible to realize an imagefiling system in which compressed moving picture information is recordedon optical disks, offering more excellent retrievability than tape mediarepresented by a conventional VTR, and which is easy to use. Since thiskind of disk filing system handles digital information, degradations dueto copying are not observed. Moreover, since optical recording/playbackis employed, a non-contacting and therefore reliable system can beconstructed.

Conventionally, recording of compressed moving picture information on anoptical disk is achieved by recording digital compressed moving pictureinformation, which conforms to the MPEG system shown in FIG. 41, in anoptical disk device shown in the block diagram of FIG. 40. Imageinformation digitized by the A/D converter 12 is transformed by theinformation compressing means 13 according to the MPEG or any otherstandard compressed moving picture system. The compressed information isencoded by the encoder 15, and modulated by the modulator 16 in order toreduce the influence of inter-code interference on the optical disk 23.The resultant information is recorded on the optical disk 23. At thistime, data is allocated such that, for example, the amount of data perGOP is substantially identical (in other words, at a fixed rate), anddata is allocated to sectors whose length is equal to an integermultiple of a frame. This facilitates GOP-by-GOP editing or the like.

For playback, image information read from the optical disk 23 isamplified by the playback amplifier 27. Digital data is then restored bythe demodulator 28 and decoder 29. Thereafter, pure and original imagedata devoid of address and parity bits is restored by the frame-sectorinverse conversion means. The information expanding means 31 performsMPEG decoding so as to restore the original digital video signal. TheD/A converter 32 provides an analog video signal that can be displayedon a monitor or the like.

Assuming that the aforesaid MPEG system is used for digital movingpicture compression, a coding scheme such as the one shown in FIG. 43 isrecorded on the optical disk 23 as it is. Herein, the coding scheme isconstructed by combining the I picture 67, which has been subjected toinformation compression based on intra-frame DCT, with several Ppictures 68 which have been subjected to information compression byintra-frame DCT and motion compensation using the temporally preceding Ipicture 67 or another P picture 68 as a reference screen, and several Bpictures 69 which have been subjected to information compression, byintra-frame DCT and motion compensation using the I and/or P pictures67, 68 as reference screens.

The P and B pictures may be coded by reference to other pictures arecoded, such that the arrow-headed lines schematically illustrating therelationship between reference pictures and the pictures (predictedpictures) coded using the reference pictures within one GOP as shown inin FIG. 43. With such an arrangement, the P and B pictures are coded byreference to other pictures within the same GOP, then the image signalwithin one GOP can be decoded independently.

An I picture 67 results from intra-frame DCT, so that an image can bereproduced using the I picture 67 alone. However, with regard to a Ppicture 68 that results from forward motion compensation, an imagecannot be reproduced until the I picture 67 is reproduced. As for a Bpicture 69 resulting from forward and backward motion compensation, animage cannot be reproduced until the preceding and succeeding I and/or Ppictures 67, 68 are reproduced. The B picture 69 resulting from forwardand backward motion compensation therefore contains the least amount ofdata and is coded most efficiently. By contrast, the I picture 67resulting from compression based solely on intra-frame DCT contains thelargest amount of data and is coded least efficiently.

Coding efficiency can be improved by increasing the number of B pictures69. Increasing the number of B pictures requires increase in the storagecapacity of a a buffer memory for storing the I and P pictures 67 and 68necessary for reproducing the B pictures 69. Moreover, a delay time fromthe input of data to image reproduction is longer. However, a greaterdemand on the storage media such as an optical disk is a highercompression efficiency to achieve a longer-time recording, and the delaytime for image reproduction does not pose a critical problem. The codingscheme shown in FIG. 43 is therefore suitable.

When data having the above coding scheme is recorded on an optical disk,fast retrieval and playback of an image are accomplished as describedbelow.

That is, when data has the coding scheme shown in FIG. 43, fast playbackis enabled by consecutively reproducing only the data representing Ipictures 67. After data representing an I picture 67 belonging to acertain GOP is reproduced, a track jump is made to another preceding orsucceeding GOP, or at an arbitrary GOP distance, to consecutivelyreproduce the data of I pictures 67, and to thereby realize fastretrieval or playback at a speed of (number of frames constituting aGOP)×(track jump distance in terms of the number of GOPs) times thenormal speed.

Recording digital video signal on recording media such as optical diskusing the data compression coding method according to the MPEG systemcan be achieved either by a method of recording the image signal data ofeach GOP as a variable amount of data, i.e., recording each GOP with avariable data rate, in order to maintain the picture quality constantbetween GOPs, as shown in FIG. 44A, or by a method of recording each GOPwith a fixed amount of data, i.e., recording each GOP with a fixed datarate, in order to maintain the recording time of each GOP constant, asshown in FIG. 10B.

The former method is advantageous in increasing the recording density onthe disk, while the latter method is advantageous in that it is easy topredict the recording position of the image data in retrieving an imagesignal at a known time from the start of the image of one sequence(title, program).

In the former method, the amount of data per GOP varies with timedepending on the nature of the pictures forming the GOP, as shown inFIG. 45A, in which (α) represents the maximum data rate and (β)represents the average data rate. For instance, the picture quality perGOP and the amount of data for each of the three types of images V1, V2and V3 are as shown in FIG. 45B. It is seen that in the former method,the picture quality is maintained constant by varying the amount of dataper GOP of the image.

A disk playback device using the image signal coding method according tothe MPEG method is a video CD (compact disc) player. FIG. 46schematically illustrates a track configuration in a video CD and a dataconfiguration within the user region of one sector in a track. A marginof a predefined number of sectors is provided at the head and tail ofeach track, and other sectors in combination form one unit oftransmission (pack) of MPEG data. Time stamp data indicating the timefrom the start of the recorded sequence (title, program) is recorded atthe head of the one pack of image data.

The method of recording each GOP with a fixed amount of data, i.e., witha fixed data rate is used for the image signal coded by the MPEG system.

In such video CD, the image signal and audio signal of one entiresequence (title, program) that are recorded are treated as one datafile. The GOPs forming the data are successively recorded in consecutivesectors on the disk as consecutive data as shown in FIG. 42. Filemanagement data such as file identification data and start sectoraddress, not shown, are recorded in the track at the head of the disk,and the access to the file consisting of the image signal and the audiosignal of the desired title can be made on the basis of the filemanagement data.

Image signal of the desired sequence (title, program) can be reproducedby successively accessing the sectors, from the sector at the head ofthe region where the file is recorded, in accordance with the startsector address of the data file corresponding to the sequence, byreferring to the file management data.

Generally, data on the recording media such as disks are physicallyrecorded in sectors forming units of recording, and recording (writing)and reproduction (reading) of data are performed taking each sector as aunit of access.

When a GOP in the middle of a sequence (title, program) is to bereproduced, a sector in the middle of the succession of the sectorswhere the data file is recorded is accessed first. However, the GOP datain the pack of each sector is recorded as consecutive data, as shown inFIG. 46, the GOP data data read first is from the middle of a GOP, andthe other part partially recorded in the immediately preceding sectorwill be dropped in the reproduced data.

Accordingly, the reference picture data used for coding P and B picturesin the GOP read first is missing, and image obtained by decoding themwould be unnatural, so that they would not be used for playback of theimage.

The GOP in the middle of a sequence (title, program), at a desired timefrom the start of the sequence is to be reproduced, the sector addresswhere the desired GOP is recorded is first predicted, on the basis ofthe fixed rate of the recorded image signal. Then, access is made to thepredicted sector address, and the signal recorded in the sector is read,and the time stamp data in it is detected. By comparing the contents ofthe detected time stamp data with the desired time instant, the sectorwhere the desired GOP is recorded is identified. Then, the GOPs aresuccessively read, from the first GOP recorded in the sector, and thetime code at the head of each GOP is detected, and when the time code isof the desired time instant, the GOP is found to be the desired GOP, andthe GOP is decoded to produce the playback image.

In a coding scheme recorded on a video disk is configured as describedabove, only I-pictures can be decoded by themselves. An image that canbe retrieved has therefore been limited to the I pictures.

Moreover, with the conventional video disk recording/playback device orplayback device, it is not possible to identify the video disk beingrecorded or played back, so that images to be retrieved, images fromwhich the playback should start, and the like are not known.

When a GOP in the middle of a sequence (title, program) is reproduced,the GOP which is read first from the sector accessed first has its partmissing, so that it would produce unnatural image if it were decoded andoutput.

Accordingly, it is not used, and as a result, there is a time delaybefore the image signal is reproduced and displayed.

Moreover, when the conventional recording method is applied to awrite-once media, and when editing, such as overwriting or tag recordingis conducted, the image signal is recorded consecutively in therecording region within the sector, so that when the GOP to beoverwritten is in the middle of the sector, and if the entire sector isoverwritten, the tail part of the GOP preceding the GOP to be editedwill be missing, and when the edit point is reproduced, the GOPpreceding the GOP having been edited will not be reproduced and theimage will be missing. Even if the reproduction is forcibly made, aresultant image would be unnatural.

Furthermore, when the conventional recording method is applied to awrite-once media, the entire sequence is treated as one file, andrecorded in consecutive sectors on the disk. During playback, theposition on the disk where the file is recorded can be identified onlyby the start sector address which is the file management data. It is notpossible to utilize, for recording and playback, vacant sectors whichresult by repeating erasure and recording. Thus, the recording regionson the disk are not effectively utilized.

In addition, when a GOP in the middle of a sequence (title, program) isreproduced, and when a GOP at a desired time from the start of thesequence is to be reproduced, it is necessary to follow a complicatedprocess wherein the sector address of the sector where the desired GOPis recorded is predicted on the basis of the data rate of the imagesignal, and by comparing the time stamp data indicating the recordingtime of the sector and desired time instant, the sector where thedesired GOP is recorded is identified, and by comparing the time code atthe head of the GOPs successively read from the sector, with the desiredtime instant, the desired GOP is identified. It is therefore notpossible to promptly identify the sector where the desired GOP isrecorded, and there is a certain time delay before the image signal isreproduced. Moreover, where the image signal of each GOP is recordedwith a variable data rate, the time from the start of the sequence andthe recording position are not proportional, so the prediction of thesector address of the sector where the GOP of the desired time instantis recorded is difficult, and there is a further delay before the imagesignal is reproduced.

Furthermore, in the conventional optical disk recording/playback devicehaving the aforesaid configuration, only the I pictures of GOPs arereproduced consecutively. When it is taken into account that human eyesare sensitive to what is called a "scene change;" such as a change instrength of a luminance signal, the fast playback or retrieval is notalways satisfactory to viewers.

In addition, as for fast playback or retrieval achieved by consecutivelyreproducing I pictures alone, positions of the I pictures in GOPs do nothave correlation to positions of the I pictures on recording tracks onan optical disk. When an image compression ratio for recording isvaried, the length of each GOP itself is not fixed. The correlationbecomes even less. When a track jump is made, it is difficult to specifya start position of an I picture of each GOP. Every time a jump is madeto another track, a random rotation wait time arises, and consecutivereproduction of I pictures cannot be made smoothly.

Furthermore, the speed of fast playback or retrieval cannot be raised inharmony with human visual characteristics.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the foregoing problems.

Another object of the present invention is to enable high high-speedretrieval of any of I, P, and B pictures during image retrieval.

Another object of the present invention is to provide a video diskrecording/playback device enabling selection of an image such as animage to be retrieved from images represented by a video signal duringrecording of the video signal on a video disk or the like.

Another object of the present invention is to enable selection of animage such as an image to be retrieved from reproduced images duringreproduction of a video signal recorded on a video disk or the like.

Another object of the present invention is to enable a user to determineor retrieve recorded contents readily by simultaneously displaying aplurality of images such as images to be retrieved that have beenrecorded on a video disk or the like.

Another object of the present invention is to enable high-speedretrieval of all kinds of images of I, P, and B pictures during imageretrieval.

A further object of the invention is to shorten the time required takenbefore reproducing the image signal and displaying it, when a codingunit, such as a GOP, which is in the middle of the image signal as awhole, such as a sequence (title, program), is to be reproduced.

Another object of the invention is to facilitate editing such asoverwriting and tag recording taking each coding unit as a unit, and toavoid dropout of playback image.

Another object of the invention is to utilize the vacant sectorsdistributed throughout the disk media, to play back.

Another object of the invention is to identify readily and promptly theposition at which the coding unit at a desired time instant is recordedand to shorten the time taken before the image signal is reproduced,when a coding unit, such as a GOP which is in the middle of the imagesignal as a whole, such as a sequence (title, program) is played back,and in particular when playback is started at a coding unit at a desiredtime from the starting point of the sequence.

A further object of the present invention is to enable fast playback orretrieval suitable to viewer's visual characteristics, to reproduceconsecutive I pictures smoothly, and to raise the speed of fast playbackor retrieval in harmony with human visual characteristics.

According to one aspect of the invention, there is provided a video diskrecording and playback method wherein a digital video signal or the likeis converted into high-efficiency coded data, and the coded data isrecorded on a video disk, or the high-efficiency coded data recorded onthe video disk or the like is restored and an output image or the likeis reproduced, wherein said digital video signal is composed of asuccession of video signals of a plurality of frames and including an Ipicture encoded within a frame, a P picture interframe coded by forwardmotion compensation with reference to said I picture and/or another Ppicture, and a B picture interframe coded by motion compensation in bothdirections with reference to said I and/or P pictures temporallypreceding and succeeding said B picture, and the start addresses ofcoded data representing selected images such as images to be retrievedand the start addresses of data containing information required forreproducing the coded data are all recorded in an image informationtable set up on said video disk.

The above recited video disk recording/playback method enables retrievalof all kinds of images of I, P, and B pictures by recording in the imageinformation table set up on the video disk all of the start addresses ofcoded data representing selected images such as images to be retrievedand the start addresses of data containing information required forreproducing the coded data.

According to another aspect of the invention, there is provided a videodisk recording/playback device for converting a digital video signal orthe like into high-efficiency coded data and recording the coded data ona video disk, or for restoring high-efficiency coded data recorded onthe video disk and reproducing an output image, wherein said digitalvideo signal is composed of a succession of video signals of a pluralityof frames and including an I picture encoded within a frame, a P pictureinterframe coded by forward motion compensation with reference to said Ipicture and/or another P picture, and a B picture interframe coded bymotion compensation in both directions with reference to said I and/or Ppictures temporally preceding and succeeding the B picture, wherein saidvideo disk recording/playback device further comprises a means forrecording in an image information table set up on said video disk all ofthe start addresses of coded data representing selected images such asimages to be retrieved and the start addresses of data containinginformation required for reproducing the coded data.

It may so arranged that said recording means records, in an imageinformation table set up on said video disk, all of said start addressesof coded data representing selected images and the start addresses ofthe data containing information required for reproducing the coded data.

The above recited video disk recording/playback device enables retrievalof all kinds of images of I, P, and B pictures by recording all of thestart addresses of coded data representing selected images such asimages to be retrieved and the start addresses of data containinginformation required for reproducing the coded data in the imageinformation table on the video disk.

The video disk recording/playback device may further comprise a meansfor selecting one of input images as a selected image during recordingof said input images on the video disk.

The above recited video disk recording/playback device enables selectionof any of images represented by an input image signal as a selectedimage such as an image to be retrieved during recording of the inputimage signal on the video disk.

The video disk recording/playback device may further comprise a meansfor selecting one of output images as a selected image duringrestoration of coded data recorded on the video disk and output of saidoutput images.

The above recited video disk recording/playback device enables selectionof any of images represented by an output signal as a selected imagesuch as an image to be retrieved during output of a video signalrecorded on the video disk.

The video disk recording/playback device may further comprise a meansfor performing low-pass filtering on selected images that have beendecoded, a means for performing sub-sampling on images that have beenfiltered, and a means for storing the images that have been obtained bythe sub-sampling, and displaying a single or a plurality of selectscreens recorded on the video disk as small screens that are N (N≧1)fractions of one screen.

The above recited video disk recording/playback device enablesidentification or retrieval of contents recorded on the video disk bydisplaying any number of selected images recorded on the video disk assmall screens that are 1/N fractions of one screen.

It may so arranged that said recording means also stores an ID signalfor identifying the video disk.

With the above arrangement, it is possible to retrieve any of the I, Pand B pictures.

According to another aspect of the invention, there is provided a videodisk playback device for playing back from a video disk on which ahigh-efficiency coded data of a digital video signal is recorded,wherein the digital video signal is a succession of image signals ofseveral frames comprising in combination an I-picture coded within theframe, a P picture inter-frame coded by forward motion compensation withreference to the I picture or another P picture, and B picturesinter-frame coded by both directional motion compensation with referenceto the I and/or P pictures positioned in front and at the back, saiddevice comprising:

means for storing a start address of the coded data of the selectedimage, a start address of the data containing information required forreproducing coded data, and an ID signal for identifying the video disk,and

means for obtaining the ID signal from the bit sequence recorded in aspecific part of the video disk.

With the above arrangement, it is possible to retrieve any of the I, Pand B pictures.

According to another aspect of the invention, there is provided a videodisk on which high-efficiency coded data transformed from a digitalvideo signal or the like is recorded, wherein said digital video signalis composed of a succession of video signals of a plurality of framesand including an I picture to be encoded within a frame, a P pictureinterframe coded by forward motion compensation with reference to said Ipicture and/or another P picture, and a B picture interframe coded bymotion compensation in both directions with reference to said I and/or Ppictures temporally preceding and succeeding the B picture, and saidvideo disk has an image information table in which the start addressesof coded data representing selected images such as images to beretrieved and the start addresses of data containing informationrequired for reproducing the coded data are all recorded.

The above recited video disk enables retrieval of all kinds of images ofI, P, and B pictures by recording in the image information table set upon the video disk all of the start addresses of coded data representingselected images such as images to be retrieved and the start addressesof data containing information required for reproducing the coded data.

According to another aspect of the invention, there is provided an imagesignal recording method in which an image signal is divided into codingunits each corresponding to a predefined number of images, and thecoding units are separately coded, and recorded onto a disk media,comprising the steps of:

generating data files for the coded data of each of coding units; and

recording the data files, from the start of the sector which is a unitof access on the disk media.

With the above arrangement, when the image signal of the coding units ata position in the middle of an image signal as a whole is reproducedfrom a disk media, the coded data in the coding unit read from thesector accessed first will not be dropped, and the decoding and outputcan be started from the coded data of the coding unit recorded at thestart of the sector without fail. As a result, the time required fromthe reproduction of the image signal and before the image is displayedcan be shortened. Moreover, when editing such as overwriting or tagrecording, taking each coding unit as a unit, it is possible to avoiddropout of the coded data of the coding units, before the editing. As aresult, editing such as overwriting or tag recording taking each codingunit as a unit can be made easily, and dropout of the image signal willnot occur when the edit point is reproduced.

It may so arranged that information indicating the order of playback isrecorded in a predefined sector region of the disk media.

With the above arrangement, during playback, the information indicatingthe order of playback of the data files is detected, and the data filescan be read according to the order of playback of data files indicatedthereby, to reproduce the image signal. As a result, the vacant sectorsdistributed over the disk media can be effectively utilized forrecording and playback.

According to another aspect of the invention, there is provided an imagesignal recording device in which an image signal is divided into codingunits each corresponding to a predefined number of images, and thecoding units are separately coded, and recorded onto a disk media,comprising:

data file generation means for generating data files for the coded dataof each of coding units;

data recording means for recording data in sectors which are units ofaccess on the disk media; and

recording control means for controlling the data recording means suchthat data files are recorded from the start of the sector.

With the above arrangement, when the image signal of the coding units ata position in the middle of an image signal as a whole is reproducedfrom a disk media, the coded data in the coding unit read from thesector accessed first will not be dropped, and the decoding and outputcan be started from the coded data of the coding unit recorded at thestart of the sector without fail. As a result, the time required fromthe reproduction of the image signal and before the image is displayedcan be shortened. Moreover, when editing such as overwriting or tagrecording, taking each coding unit as a unit, it is possible to avoiddropout of the coded data of the coding units, before the editing. As aresult, editing such as overwriting or tag recording taking each codingunit as a unit can be made easily, and dropout of the image signal willnot occur when the edit point is reproduced.

The image signal recording device may further comprise playback orderinformation generating means for generating information indicating theorder of playback of the data files, said recording means controls thedata recording means such that the information indicating the order ofplayback of the data files generated by the playback order informationgenerating means is recorded in a predefined section region on the diskmedia.

With the above arrangement, during playback, the information indicatingthe order of playback of the data files is detected, and the data filescan be read according to the order of playback of data files indicatedthereby, to reproduce the image signal. As a result, the vacant sectorsdistributed over the disk media can be effectively utilized forrecording and playback.

According to another aspect of the invention, there is provided an imagesignal playback method of playing back image signal in coding unitspositioned in the middle of the image signal as a whole, from a diskmedia on which data files formed for each coded data, obtained bydividing an image signal into coding units each corresponding to apredefined number of images, and separately coding the coding units,comprising the steps of:

reading data from sector group in which data files are generated fromthe coded data in the coding units positioned in the middle within theimage signal as a whole;

restoring the coding units obtained by coding from the start of thecoded data read from the sector recorded first, among the sector group;and

decoding and outputting the coding data in the coding units having beenrestored.

With the above arrangement, even when the coding units at a position inthe middle of the image signal as a whole is to be reproduced, it is notnecessary to consider the dropout of the coded data, and the coded dataread from the sector recorded first can be taken as the first image forplayback and display. As a result, the time required from thereproduction of the image signal and before the image is displayed canbe shortened. Moreover, when editing such as overwriting or tagrecording, taking each coding unit as a unit, it is possible to avoiddropout of the coded data of the coding units, before the editing. As aresult, editing such as overwriting or tag recording taking each codingunit as a unit can be made easily, and dropout of the image signal willnot occur when the edit point is reproduced.

According to another aspect of the invention, there is provided an imagesignal playback device for playing back image signal in coding unitsfrom a disk media on which data files formed for each coded data,obtained by dividing an image signal into coding units eachcorresponding to a predefined number of images, and separately codingthe coding units, comprising

data read means for reading data from the sector;

read control means for generating sector addresses of the sectors to beaccessed, and controlling the data read means such that it reads thedata from the sectors of the sector addresses; and

coding unit restoring means for restoring the coding units from thecoded data having read by means of the data read means;

wherein when the image signal in the coding units positioned in themiddle of the image signal as a whole is played back, said read controlmeans generates sector address group recorded in the data file in whichthe coding unit in question is contained, and

said coding unit restoring means restores the coding units from thestart of the coded data having been read by the read means, from thesector in which the data filed is first recorded, of the sector groupcorresponding to the sector address group.

With the above arrangement, even when the coding units at a position inthe middle of the image signal as a whole is to be reproduced, it is notnecessary to consider the dropout of the coded data, and the coded dataread from the sector recorded first can be taken as the first image forplayback and display. As a result, the time required from thereproduction of the image signal and before the image is displayed canbe shortened. Moreover, when editing such as overwriting or tagrecording, taking each coding unit as a unit, it is possible to avoiddropout of the coded data of the coding units, before the editing. As aresult, editing such as overwriting or tag recording taking each codingunit as a unit can be made easily, and dropout of the image signal willnot occur when the edit point is reproduced.

According to another aspect of the invention, there is provided an imagesignal playback method of playing back image signal from a disk media onwhich data files formed for each coded data, obtained by dividing animage signal into coding units each corresponding to a predefined numberof images, and separately coding the coding units, and informationindicating the order of playback of the data files is recorded in apredefined sector region, comprising the steps of:

detecting information indicating the order of playback of the datafiles, from the data read from the predefined sector region;

reading data files from the disk media on the basis of the informationindicating the order of playback of the data files having been detected;and

decoding the coded data in the coding units contained in the data filehaving been read, so as to reproduce image data.

With the above arrangement, the image signal recorded in the sectorsdistributed over the disk media can be reproduced, and vacant sectorsdistributed over the disk media can be utilized effectively forrecording and playback.

According to another aspect of the invention, there is provided an imagesignal playback device for playing back image signal from a disk mediaon which data files formed for each coded data, obtained by dividing animage signal into coding units each corresponding to a predefined numberof images, and separately coding the coding units, and informationindicating the order of playback of the data files is recorded in apredefined sector region, comprising the steps of:

data read means for reading data from the sector;

read control means for generating sector addresses of the sectors to beaccessed, and controlling the data read means such that it reads thedata from the sector of the sector address;

playback order information detecting means for detecting the informationindicating the order of playback of the data files from the data read bymeans of the read means; and

decoding means for decoding the coded data in the coding units containedin the data file having been read by means of the read means;

wherein when the playback is started said read control means generatessector addresses of the predefined sector region in which theinformation indicating the order of playback of the data files isrecorded, and

after the playback order information is detected by the playback orderinformation detecting means from the data having been read from the databy the data read means, the sector addresses are generated on the basisof the playback order information detecting means.

With the above arrangement, the image signal recorded in the sectorsdistributed over the disk media can be reproduced, and vacant sectorsdistributed over the disk media can be utilized effectively forrecording and playback.

According to another aspect of the invention, there is provided a Animage signal recording method of recording image signal after dividingthe image signal into coding units each corresponding to a predefinednumber of images, and separately coding the coding units, comprising thesteps of:

generating a data file for each of the coded data in the coding unit;

generating data file identification information indicating a positionwithin the image signal as a whole and a position of recording on thedisk media, for each data file corresponding to the coding unit; and

recording the data file and the data file identification information inthe respective predefined regions of the disk media.

With the above arrangement, when the image signal of the coding unit ata position in the middle of the image signal as a whole is reproduced,it is possible to readily and promptly identify the position on the diskmedia where the desired coding unit is recorded, by detecting the datafile identification information, so that the time required for thereproduction of the image signal can be shortened.

According to another aspect of the invention, there is provided an imagesignal recording device for recording coding units each corresponding toa predefined number of images, and separately coding the coding units,and recording the coding units on a disk media, comprising:

data file generating means for generating data file for each coding datain the coding unit;

data file identification means for generating data file identificationinformation a position within the image signal as a whole and a positionof recording on the disk media, for each data file corresponding to thecoding unit;

data recording means for recording the data in the sector which is aunit of access on the disk media; and

recording control means for controlling the data recording means suchthat it records the data file and the data file identificationinformation in the respective predefined regions of the disk media.

With the above arrangement, when the image signal of the coding unit ata position in the middle of the image signal as a whole is reproduced,it is possible to readily and promptly identify the position on the diskmedia where the desired coding unit is recorded, by detecting the datafile identification information, so that the time required for thereproduction of the image signal can be shortened.

According to another aspect of the invention, there is provided an imagesignal playback method of playing back image signal in the coding unitspositioned in the middle of the image signal as a whole, from a diskmedia in which data files containing signals obtained by coding thecoding units consisting of image signals of a predefined number ofimages and data file information indicating the position within theimage signal as a whole and the recording position on the disk media foreach of the data files corresponding to the coding units are recorded inrespective predefined sector regions of the disk media, comprising thesteps of:

inputting the position identification signal indicating the position ofthe coding unit to be reproduced, within the image signal as a whole;

detecting the data file identification signal from the signals read fromthe predefined sector regions on the disk media;

identifying the recording position on the disk media of the data filecorresponding to the coding unit which is at a position indicated by theposition identification signal;

reading the data file on the basis of the position on the disk mediathat has been identified; and

decoding the signal coded for each coding unit, contained in the datafile having been read, and reproducing an image signal.

With the above arrangement, it is possible to readily and promptlyidentify the position in which a certain coding unit is recorded at adesired time instant, and it is possible to shorten the time requiredfor the reproduction of the image signal.

According to another aspect of the invention, there is provided an imagesignal playback device of playing back image signal from a disk media inwhich data files containing signals obtained by coding the coding unitsconsisting of image signals of a predefined number of images and datafile information indicating the position within the image signal as awhole and the recording position on the disk media for each of the datafiles corresponding to the coding units are recorded in respectivepredefined sector regions of the disk media, comprising the steps of:

position identification signal input means for inputting the positionidentification signal indicating the position of the coding unit to bereproduced, within the image signal as a whole;

data read means for reading data from the sector of the disk media;

read control means for generating the sector address of the sectors tobe accessed and controlling the data read means such that it reads thedata from the sectors of the sector addresses;

data file identification information detecting means for detecting thedata file identification information from the data read by the data readmeans;

recording sector identification means for identifying the sector inwhich the data file is recorded on the disk media, on the basis of thedata file identification information; and

decoding means for decoding the signal coded in the coding units,contained in the data file having been read, and reproducing the imagesignal;

wherein when the image signal in the coding units positioned in themiddle within the image signal as a whole is reproduced, said recordingsector identification means identifies the sector in which the data filecorresponding to the coding unit at a position indicated by the positionidentification signal input by means of the position identificationsignal input means is recorded;

said read control means generates sector addresses on the basis of thesector in which the data file corresponding to the coding unit at aposition indicated by the position identification signal identified bythe recording sector identification means is recorded.

With the above arrangement, it is possible to readily and promptlyidentify the position in which a certain coding unit is recorded at adesired time instant, and it is possible to shorten the time requiredfor the reproduction of the image signal.

According to another aspect of the invention, there is provided an Animage signal recording disk media in which data file generated for eachcoding data obtained by dividing an image signal into coding units of apredefined number of images and coding each coding unit separately isrecorded from the start of the sector which is a unit of access.

With the above arrangement, when the image signal of the coding units ata position in the middle of an image signal as a whole is reproducedfrom a disk media, the coded data in the coding unit read from thesector accessed first will not be dropped, and the decoding and outputcan be started from the coded data of the coding unit recorded at thestart of the sector without fail. As a result, the time required fromthe reproduction of the image signal and before the image is displayedcan be shortened. Moreover, when editing such as overwriting or tagrecording, taking each coding unit as a unit, it is possible to avoiddropout of the coded data of the coding units, before the editing. As aresult, editing such as overwriting or tag recording taking each codingunit as a unit can be made easily, and dropout of the image signal willnot occur when the edit point is reproduced.

It may so arranged that information indicating the order of playback ofthe data files is recorded in a predefined sector region.

With the above arrangement, during playback, the information indicatingthe order of playback of the data files is detected, and the data filescan be read according to the order of playback of data files indicatedthereby, to reproduce the image signal. As a result, the vacant sectorsdistributed over the disk media can be effectively utilized forrecording and playback.

According to another aspect of the invention, there is provided an imagesignal recording disk media wherein data file containing the signalobtained by coding the coding units consisting of an image signal of apredefined number of images and data file identification informationindicating the position within the image signal as a whole and therecording position on the disk media, for each of data filescorresponding to the coding units are recorded in respective predefinedsector regions on the disk media.

With the above arrangement, when the image signal of the coding unit ata position in the middle of the image signal as a whole is reproduced,it is possible to readily and promptly identify the position on the diskmedia where the desired coding unit is recorded, by detecting the datafile identification information, so that the time required for thereproduction of the image signal can be shortened.

According to another aspect of the invention, there is provided anoptical disk recording/playback device comprising:

an A/D conversion means for sampling an input image signal at a giveninterval so as to produce frame images;

an information compressing means for constructing an image informationblock using several consecutive frames images to several tens ofconsecutive frame images, performing information compression on part offrame images constituting said image information block so as to producea two-dimensionally compressed frame image, and performing informationcompression on the remaining frame images according to motion vectorsdetected between said frame images so as to produce three-dimensionallycompressed frame images;

a scene change detecting means for detecting a scene change between saidimage information blocks on the basis of frame images obtained bysampling said image information blocks at a given interval;

a recording means for recording image information blocks having beensubjected to the information compression by said information compressingmeans and scene change information detected by said scene changedetecting means, on an optical disk; and

a reproducing means for consecutively reproducing the two-dimensionallycompressed frame images of said image information blocks, for whichscene changes have occurred, according to said scene change informationrecorded on said optical disk.

With the above arrangement, address information of the two-dimensionallycompressed frame images of image information blocks for which scenechanges have occurred is recorded on an optical disk together with theimage information blocks, data at positions specified with the addressinformation is consecutively reproduced during playback, and thus fastplayback or retrieval of an image signal is achieved.

It may be so arranged that the positions of the two-dimensionallycompressed frame image and three-dimensional frame images in each imageinformation block can be varied, and the frame images can be divided,and therefore the start positions of the two-dimensionally compressedframe images of the image information blocks are aligned alongpredetermined radial lines of the optical disk on recording tracksthereof.

With the above arrangement, the positions of two-dimensional andthree-dimensionally compressed frame images in each image informationblock can be varied, and compressed frame images can be divided, and thestart positions of the two-dimensionally compressed images of imageinformation blocks will always coincide with specific positions on anoptical disk. The randomness of a rotation wait time associated with atrack jump during fast playback or retrieval can therefore beeliminated.

It may be so arranged that a plurality of threshold levels are definedfor scene change detection, scene change information acquired using therespective threshold levels is recorded on said optical disk, and onlythe two-dimensionally compressed frame images of image informationblocks for which scene changes have occurred using the scene changeinformation corresponding to the selected threshold levels arereproduced consecutively.

With the above arrangement, a plurality of threshold values are definedfor scene change detection. Fast playback or retrieval of an imagesignal can therefore be achieved at different speeds.

It may be so arranged that scene change information detected by saidscene change detecting means is recorded in a given area defined alongan inner or outer circumference of said optical disk, a header part ofthe two-dimensionally compressed frame image is used for recording anaddress information indicating the position of the two-dimensionallycompressed frame image contained in an image information block adjoiningan image information block containing the two-dimensionally compressedframe image, and either of a scene change playback mode, in which onlythe two-dimensionally compressed frame images of image informationblocks for which scene changes have been detected are reproducedconsecutively from said optical disk according to said scene changeinformation, or an adjoining image information block playback mode, inwhich the two-dimensionally compressed frame images of adjoining imageinformation blocks are reproduced consecutively from said optical diskaccording to said address information, can be selected.

With the above arrangement, address information of the two-dimensionallycompressed frame images of image information blocks for which scenechanges have been detected, and address information of thetwo-dimensionally compressed frame images of adjoining image informationblocks are recorded mutually independently on an an optical disk. Forplayback, either of the address information can be selected according tothe purpose of use to achieve fast playback or retrieval of an imagesignal.

According to another aspect of the invention, there is provided anoptical disk recording device comprising:

an A/D conversion means for sampling an input image signal at a giveninterval so as to produce frame images;

an information compressing means for constructing one image informationblock using several consecutive frame images to several tens consecutiveframe images, performing information compression on part of frame imagesconstituting said image information block so as to produce atwo-dimensionally compressed frame image, and performing informationcompression on the remaining frame images according to motion vectorsdetected between said frame images so as to produce three-dimensionallycompressed frame images;

a scene change detecting means for detecting a scene change between saidimage information blocks on the basis of frame images obtained bysampling said image information blocks at a given interval; and

a recording means for recording image information blocks having beensubjected to information compression by said information compressingmeans and scene change information detected by said scene changedetecting means, on an optical disk.

With the above arrangement, address information of the two-dimensionallycompressed frame images of image information blocks for which scenechanges have occurred is recorded on an optical disk together with theimage information blocks.

It may be so arranged that the positions of the two-dimensionallycompressed frame image and three-dimensionally compressed frame imagesin each image information block can be varied, frame images can bedivided, and image information blocks are recorded in such a way thatthe start positions of the two-dimensionally compressed frame images ofimage information blocks are aligned along predetermined radial lines ofsaid optical disk on recording tracks thereof.

With the above arrangement, the positions of two-dimensionally andthree-dimensionally compressed image frames in each image informationblock can be varied, and compressed image frames can be divided, so thatthe start positions of the two-dimensionally compressed frame images ofimage information blocks will always coincide with specific positions onan optical disk.

It may be so arranged that a plurality of threshold levels are definedfor scene change detection, and scene change information acquired forthe respective threshold levels is recorded on said optical disk.

With the above arrangement, scene change information is detected andrecorded for a plurality of threshold values.

It may be so arranged that said scene change information detected bysaid scene change detecting means is recorded in a given area definedalong an inner or outer circumference of said optical disk, and a headerpart of the two-dimensionally compressed frame image is used forrecording an address information indicating the position of thetwo-dimensionally compressed frame image contained in an imageinformation block adjoining an image information block containing thetwo-dimensionally compressed frame image.

With the above arrangement, address information of the two-dimensionallycompressed frame images of image information blocks for which scenechanges have been detected and address information of thetwo-dimensionally compressed frame images of adjoining image informationblocks are mutually independently recorded on an optical disk.

According to another aspect of the invention, there is provided anoptical disk playback device for reproducing images from an optical diskon which image information blocks each serving as a recording unitformed by combining several frames to several tens of frames of I, P andB pictures, with an I picture being a frame image having been obtainedby two-dimensional information compression based on frequencytransformation, and P and B pictures that are frame images having beenobtained by three-dimensional information compression based on frequencytransformation and motion-compensated prediction, and scene changeinformation detected between said image information blocks are recorded,and comprising:

a scene change reproducing means for reproducing said scene changeinformation from said optical disk; and

an image reproducing means for consecutively reproducing only the Ipictures of image information blocks for which scene changes have beendetected, according to reproduced scene change information.

With the above arrangement, based on address information of I picturesof image information blocks which are recorded on an optical disk andfor which scene changes have occurred, the I pictures alone areconsecutively reproduced to thus achieve fast playback or retrieval ofan image signal.

It may be so arranged that the start positions of the I pictures ofimage information blocks recorded on said optical disk are aligned alonggiven radial lines of said optical disk on recording tracks thereof.

With the above arrangement, the start positions of I pictures of imageinformation blocks always coincide with specific positions on an opticaldisk. The randomness of a rotation wait time associated with a trackjump during fast playback or retrieval can therefore be eliminated.

It may be so arranged that said scene change information is detectedbetween image information blocks for a plurality of threshold levels,said scene change reproducing means reproduces scene change informationfor a threshold level selected by a selecting means, and consecutivelyreproduces from said optical disk only the I pictures of imageinformation blocks for which scene changes have been detected, accordingto said scene change information.

With the above arrangement, I pictures selected according to scenechange information detected for a plurality of thresholds areconsecutively reproduced. Fast playback or retrieval of an image signalcan therefore be achieved at different speeds.

It may be so arranged that said scene change information is recorded ina given area defined along an inner or outer circumference of saidoptical disk, a header part of the I picture is used for recording theaddress information indicating the position of an I picture contained inan image information block adjoining an image information blockcontaining the I picture, and said optical disk reproducing devicefurther comprises a mode selecting means for use in selecting either ofa scene change playback mode, in which only the I pictures of imageinformation blocks for which scene changes have been detected areconsecutively reproduced from said optical disk according to said scenechange information, or an adjoining image information block playbackmode, in which I pictures of adjoining image information blocks areconsecutively reproduced from said optical disk according to saidaddress information.

With the above arrangement, either a scene change playback mode, inwhich only the I pictures of image information blocks for which scenechanges have been detected are consecutively reproduced, or an adjoiningimage information block playback mode, in which I pictures of adjoiningimage information blocks are consecutively reproduced, can be selectedaccording to the purpose of use.

According to another aspect of the invention, there is provided anoptical disk recording/playback method comprising the step of:

sampling an input image signal at a given interval so as to produceframe images, constructing one image information block using images ofseveral consecutive frame images to several tens of consecutive frameimages, performing information compression on part of frame imagesconstituting said image information block so as to produce atwo-dimensionally compressed frame image, and performing informationcompression on the remaining frame images according to motion vectorsdetected between said frame images so as to produce three-dimensionallycompressed frame images;

detecting a scene change between said image information blocks on thebasis of frame images obtained by sampling said image information blocksat a given interval;

recording image information blocks subjected to said informationcompression and scene change information on an optical disk; and

consecutively reproducing only the two-dimensionally compressed frameimages of said image information blocks for which scene changes haveoccurred, according to scene change information recorded on said opticaldisk.

With the above arrangement, address information of the two-dimensionallycompressed frame images of image information blocks for which scenechanges have occurred is recorded on an optical disk together with theimage information blocks, data at positions specified with the addressinformation is consecutively reproduced during playback, and thus fastplayback or retrieval of an image signal is achieved.

It may be so arranged that the positions of the two-dimensionallycompressed frame image and three-dimensionally compressed frame imagesin each image information block can be varied, frame images can bedivided, and the start positions of the two-dimensionally compressedframe images of image information blocks are aligned along predeterminedradial lines of said optical disk on recording tracks thereof.

With the above arrangement, the positions of two-dimensional andthree-dimensionally compressed frame images in each image informationblock can be varied, and compressed frame images can be divided, and thestart positions of the two-dimensionally compressed images of imageinformation blocks will always coincide with specific positions on anoptical disk. The randomness of a rotation wait time associated with atrack jump during fast playback or retrieval can therefore beeliminated.

It may be so arranged that a plurality of threshold levels are definedfor scene change detection, scene change information acquired for therespective threshold levels is recorded on said optical disk, and onlythe two-dimensionally compressed frame images of image informationblocks for which scene changes have occurred are reproducedconsecutively according to scene change information associated with aselected threshold level.

With the above arrangement, a plurality of threshold values are definedfor scene change detection. Fast playback or retrieval of an imagesignal can therefore be achieved at different speeds.

It may be so arranged that scene change information detected by saidscene change detecting means is recorded in a given area defined alonean inner or outer circumference of said optical disk, a header part ofthe two-dimensionally compressed frame image is used for recording anaddress information indicating the position of the two-dimensionallycompressed frame image contained in an image information block adjoiningan image information block containing the two-dimensionally compressedframe image, either a scene change playback mode, in which only thetwo-dimensionally compressed frame images of image information blocksfor which scene changes have been detected are consecutively reproducedfrom said optical disk according to said scene chance information, or anadjoining image information block playback mode, in which thetwo-dimensionally compressed frame images of adjoining image informationblocks are consecutively reproduced from said optical disk according tosaid address information, can be selected.

With the above arrangement, address information of the two-dimensionallycompressed frame images of image information blocks for which scenechanges have been detected, and address information of thetwo-dimensionally compressed frame images of adjoining image informationblocks are recorded mutually independently on an optical disk. Forplayback, either of the address information can be selected according tothe purpose of use to achieve fast playback or retrieval of an imagesignal.

According to another aspect of the invention, there is provided anoptical disk recording method comprising the steps of:

sampling an input image signal at a given interval so as to produceframe images;

constructing one image information block using several consecutive frameimages to several tens of consecutive frame images, performinginformation compression on part of frame images constituting said imageinformation block so as to produce a two-dimensionally compressed frameimage, and performing information compression on the remaining frameimages according to motion vectors detected between said frame images soas to produce three-dimensionally compressed frame images;

detecting a scene change between said image information blocks on thebasis of frame images obtained by sampling said image information blocksat a given interval; and

recording image information blocks subjected to information compressionand scene change information on an optical disk.

With the above arrangement, address information of the two-dimensionallycompressed frame images of image information blocks for which scenechanges have occurred is recorded on an optical disk together with theimage information blocks.

It may be so arranged that the positions of the two-dimensionallycompressed frame image and three-dimensionally compressed frame imagesin each image information block can be varied, frame images can bedivided, and image information blocks are recorded in such a way thatthe start positions of the two-dimensionally compressed frame images ofimage information blocks are aligned along predetermined radial lines ofsaid optical disk on recording tracks thereof.

With the above arrangement, the positions of two-dimensionally andthree-dimensionally compressed image frames in each image informationblock can be varied, and compressed image frames can be divided, so thatthe start positions of the two-dimensionally compressed frame images ofimage information blocks will always coincide with specific positions onan optical disk.

It may be so arranged that a plurality of threshold levels are definedfor scene change detection at said scene change detecting step, andscene change information acquired for the threshold levels is recordedon said optical disk.

With the above arrangement, scene change information is detected andrecorded for a plurality of threshold values.

It may be so arranged that said scene change information is recorded ina given area along an inner or outer circumference of said optical disk,and a header part of the two-dimensionally compressed frame imageinformation is used for recording the position of a two-dimensionallycompressed image contained in an image information block adjoining animage information block containing the two-dimensionally compressedimage.

With the above arrangement, address information of the two-dimensionallycompressed frame images of image information blocks for which scenechanges have been detected and address information of thetwo-dimensionally compressed frame images of adjoining image informationblocks are mutually independently recorded on an optical disk.

According to another aspect of the invention, there is provided anoptical disk playback method for reproducing images from an optical diskon which image information blocks each serving as a recording unitformed by combining several frames to several tens of frames of I, P andB pictures, with an I picture being a frame image having been obtainedby two-dimensional information compression based on frequencytransformation, and P and B pictures that are frame images having beenobtained by three-dimensional information compression based on frequencytransformation and motion-compensated prediction, and scene changeinformation detected between said image information blocks are recorded,and comprising the steps of:

reproducing said scene change information from said optical disk, and

consecutively reproducing only the I pictures of image informationblocks for which scene changes have been detected, according to saidreproduced scene change information.

With the above arrangement, based on address information of I picturesof image information blocks which are recorded on an optical disk andfor which scene changes have occurred, the I pictures alone areconsecutively reproduced to thus achieve fast playback or retrieval ofan image signal.

It may be so arranged that the start positions of I pictures of imageinformation blocks recorded on said optical disk are aligned alongpredetermined radial lines of said optical disk on recording tracksthereof.

With the above arrangement, the start positions of I pictures of imageinformation blocks always coincide with specific positions on an opticaldisk. The randomness of a rotation wait time associated with a trackjump during fast playback or retrieval can therefore be eliminated.

It may be so arranged that said scene change information is detected fora plurality of threshold levels, scene change information associatedwith a selected threshold level is reproduced, and only the I picturesof image information blocks for which scene changes have been detectedare consecutively reproduced from said optical disk according to saidscene change information.

With the above arrangement, I pictures selected according to scenechange information detected for a plurality of thresholds areconsecutively reproduced. Fast playback or retrieval of an image signalcan therefore be achieved at different speeds.

It may be so arranged that said scene change information is recorded ina given area defined along an inner or outer circumference of saidoptical disk, a header part of the I picture is used for recording theaddress information indicating the position of an I picture contained inan image information block adjoining an image information blockcontaining the I picture, and either a scene change playback mode, inwhich only the I pictures of image information blocks for which scenechanges have been detected are consecutively reproduced from saidoptical disk according to said scene change information, or an adjoiningimage information block playback mode, in which I pictures of adjoiningimage information blocks are consecutively reproduced from said opticaldisk according to said address information, can be selected.

With the above arrangement, either a scene change playback mode, inwhich only the I pictures of image information blocks for which scenechanges have been detected are consecutively reproduced, or an adjoiningimage information block playback mode, in which I pictures of adjoiningimage information blocks are consecutively reproduced, can be selectedaccording to the purpose of use.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1A shows the data structure of coded data recorded on a video diskaccording to Embodiment A1;

FIG. 1B is a schematic diagram of an image information table recorded ona video disk according to Embodiment A1;

FIG. 2 is a block circuit diagram showing a video diskrecording/playback device in accordance with Embodiment A2;

FIG. 3 is a flowchart describing the operations for image retrievalperformed by the video disk recording/playback device in accordance withEmbodiment A2, A3 or A4;

FIG. 4 is a block circuit diagram showing a video diskrecording/playback device in accordance with Embodiment A3;

FIG. 5 is a block circuit diagram showing a video diskrecording/playback device in accordance with Embodiment A4;

FIG. 6 is a block circuit diagram showing a video diskrecording/playback device in accordance with Embodiment A5;

FIG. 7 is a flowchart describing the operations for list image displayperformed by the video disk recording/playback device in accordance withEmbodiment A5;

FIG. 8 shows a list display image produced by the video diskrecording/playback device in accordance with Embodiment A5;

FIG. 9 shows a disk format for a video disk in accordance withEmbodiment A6;

FIG. 10 is a block circuit diagram showing a video diskrecording/playback device of Embodiment B1;

FIG. 11 is a diagram for explaining the operation of Embodiment B1;

FIG. 12 is a flowchart showing the operation of during image retrievalof Embodiment B1, Embodiment B2 and Embodiment B3;

FIG. 13 is a block circuit diagram showing the video diskrecording/playback device of Embodiment B2;

FIG. 14 is a block circuit diagram showing the video diskrecording/playback device of Embodiment B3;

FIG. 15 is a block circuit diagram showing the video diskrecording/playback device of Embodiment B4;

FIG. 16 is a flowchart showing the operation during list image displayaccording to Embodiment B4;

FIG. 17 is a block circuit diagram showing the video disk playbackdevice of Embodiment B5;

FIG. 18 is a flowchart showing the operation of during image retrievalof Embodiment B5 and Embodiment B6;

FIG. 19 is a block circuit diagram showing the video disk playbackdevice of Embodiment B6;

FIG. 20 is a block circuit diagram showing the video disk playbackdevice of Embodiment B7;

FIG. 21 is a flowchart showing the operation during list image displayaccording to Embodiment B7;

FIG. 22 is a block diagram showing the configuration of the image signalrecording device and image signal playback device according toEmbodiment C1;

FIG. 23 is a sector map diagram showing the arrangement of the regionson the optical disk according to Embodiment C1;

FIG. 24 is a diagram showing the configuration of the GOP informationtable data according to Embodiment C1;

FIG. 25 is a diagram showing the configuration of the GOP file sequencetable data according to Embodiment C1;

FIG. 26 is a schematic diagram showing the state of access of theoptical disk during playback according to Embodiment C1;

FIG. 27 is a schematic diagram showing the state of recording of the GOPfiles for which editing in GOP units according Embodiment C1;

FIG. 28 is a block diagram showing the configuration of a recordingsystem of an optical disk recording/playback device according toEmbodiment D1;

FIG. 29 shows data structures on data tracks which are recorded by anoptical disk recording/playback device in accordance with Embodiment D1;

FIG. 30 is a schematic diagram showing a frame structure attained whenoriginal images are sampled at a certain frame rate;

FIG. 31 shows the relationship between the distribution of absolutevalues of differences in luminance signal level between adjoining framesand the threshold which is used for scene change detection;

FIG. 32 shows the arrangement of data tracks on an optical disk;

FIG. 33 shows arrangement of data on data tracks which is recorded by anoptical disk recording/playback device in accordance with Embodiment D2;

FIG. 34 is schematic diagram showing a frame structure attained whenoriginal images are, sampled at a certain frame rate;

FIG. 35 shows the relationship between the distribution of absolutevalues of differences in luminance signal level between adjoining framesand the thresholds which are used for scene change detection;

FIG. 36 shows the relationship between image information blocks on anoptical disk and a scene change address area;

FIG. 37 shows a specific structure of the scene change address area;

FIG. 38 shows arrangement of data on data tracks which is recorded by anoptical disk recording/playback device in accordance with Embodiment D4;

FIG. 39 is a flowchart showing specific operations of Embodiment D4;

FIG. 40 is a block diagram showing the configuration of a conventionaloptical disk recording/playback device;

FIG. 41 shows data arrangement of a video signal conformable to the MPEGsystem;

FIG. 42 is a data configuration diagram showing the sequence layeraccording to the coding method according to the MPEG system;

FIG. 43 is a structure diagram showing the configuration of the GOPaccording to the coding method according the MPEG system;

FIG. 44A is a schematic diagram showing a method of recording, with avariable rate, GOPs coded by the MPEG system;

FIG. 44B is a schematic diagram showing a method of recording, with afixed rate, GOPs coded by the MPEG system;

FIG. 45A a diagram showing an example of timewise variation of theamount of data per GOP according the method of recording according tothe MPEG system;

FIG. 45B is a diagram showing the relationships between the amount ofdata per GOP and the picture quality; and

FIG. 46 is a diagram showing an example of the relationship between thepicture quality after the decoding of the image signal coded accordingto the MPEG system and the amount of data per GOP.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment A1

FIG. 1A and FIG. 1B are diagrams for explaining a video diskrecording/playback method of Embodiment A1. FIG. 1A is a schematicdiagram showing the data structure of coded data recorded on a videodisk. Reference numeral 101 denotes a sequence header. 102 denotes aGOP. 103 denotes a GOP header. 107 denotes the start address of thesequence header 101. 108 denotes the start address of the GOP header103. 109 denotes the start address of a B6 picture.

FIG. 1B is a schematic diagram showing an image information tablerecorded on the video disk. Reference numeral 110 denotes a column inwhich selected image numbers assigned to the respective selected imagesare written. 111 denotes a column in which start addresses of sequenceheaders concerning sequences each containing a selected image arewritten. 112 denotes a column in which start addresses of GOPs eachcontaining a selected image are written. 113 denotes a column in whichstart addresses of coded data representing selected images are written.

Next, the operations will be described. A collection of a plurality ofinput images are referred to as a GOP (group of pictures). Each GOPincludes the following; an I picture 104 intra-frame coded, P pictures105 inter-frame coded by forward motion compensation, and B pictures 106inter-frame coded by forward and backward motion compensation. Inputimage information composed of a succession of GOPs 102 ishigh-efficiency coded. A GOP header 103 representing informationrequired for decoding the GOP 102 is appended to the coded datarepresenting the GOP. A collection of the GOPs 102 is referred to as asequence. A sequence header 101 describing information representing, forexample, a screen size of the sequence may be appended to the start ofthe sequence. Coded data consisting of these data items is recorded on avideo disk on which addresses are assigned to areas.

For playback, the inverse of the foregoing recording procedure iscarried out. Thus, a video signal recorded on the video disk isreproduced and displayed.

Assuming that a B6 picture 106 is a selected image, a I1 picture 104 andP4, picture 105 must be decoded first in order to decode the B6 picture106. For decoding the P4 picture 105, the I1 picture 104 must be decodedfirst. Since information required for decoding the I1 picture 104 isdescribed in the GOP header 103, the information residing in the GOPheader 103 is necessary. Normally, each GOP 102 contains only one Ipicture, at a position succeeding the GOP header 103. Consequently, fordisplaying the B6 picture 106 as a selected image, the GOP 102containing the B6 picture 106 should be read starting from the GOPheader 103. The I1 picture, B2 picture, B3 picture, etc. are thendecoded in that order, until the B6 picture 106 is decoded. The picturesare then displayed. Therefore, the start address (which in theillustrated example is "0070") 109 on the disk at which the coded datarepresenting the B6 picture 106 is recorded, and the start address(which in the illustrated example is "0035") 108 of the GOP header ofthe GOP 102 containing the B6 picture 106 are necessary.

The address information is stored, for example, in a memory in thedevice. A user, for instance, may record the address information in theimage information table set up on the video disk at a desired timeinstant.

At this time, since information residing in the sequence header 101,which is required for decoding the B6 picture 106, may also becomenecessary, the start address 107 of the sequence header 101 is recordedtogether with the address information in the table. FIG. 1B shows theimage information table thus recorded on the video disk.

For retrieving the B6 picture 106 from the video disk on which data isrecorded according to the aforesaid procedure, the operations describedbelow are carried out. First, when a retrieval instruction is issued,access is gained to the image information table on the disk. The imageinformation table is then referenced to read the start address 109 onthe disk at which the coded data representing the B6 picture 106 isrecorded, the start address 108 of the GOP header of the GOP 102containing the B6 picture 106, and, if necessary, the start address 107of the sequence header. A Jump is then made to the sequence header 101,or GOP header 103, whereby information written in the header isacquired. Decoding is performed sequentially starting from the I1picture 104. When decoding of the B6 picture 106 is completed, thedecoded screen of the B6 picture 106 is displayed. Thus, retrieval isterminated.

In this example, the B6 picture 106 is specified as a selected image.Even when any other picture is specified, the aforesaid procedure isrepeated.

The leading B pictures of a GOP; that is, B2 and B3 pictures must bedecoded using the I picture or P picture at the tail of the precedingGOP. The independence of each GOP is therefore impaired. For preventingthe impairment, information indicating that such B pictures shall bedecoded through backward compensation must be appended to the GOPheader. In Embodiment A2, therefore, the B pictures are predicted usingthe I1 picture 104 alone.

Embodiment A2

FIG. 2 is a block circuit diagram showing a video diskrecording/playback device of Embodiment A2. As illustrated, it comprisesan encoder 204, a modulator 205, a laser drive circuit 206, a controlcircuit 220, an optical head 208, an actuator 209, a disk motor 211, anoptical disk 212, an address memory 223 for storing the start addressesof coded data representing selected images such as images to beretrieved and the start addresses of data including information requiredfor decoding the coded data, and a switch 224 to be manipulated forrecording the contents of the address memory 223 into the optical disk212 at a user's desired time instant.

The device further comprises a playback amplifier 213, a demodulator214, a decoder 215, an information expanding means 217, and a D/Aconverter 218 which outputs an output image signal 219.

Next, the operations will be described. High-efficiency coded datarepresenting an image and having the GOP structure described inconjunction with Embodiment A1 is recorded on the optical disk 212. AGOP header 103 containing information required for decoding each GOP 102is appended to the start of each GOP 102. A sequence header 101containing information concerning a sequence composed of a plurality ofGOPs 102 may be appended to the start of the sequence.

For reproducing data from the optical disk 212, a compressed videosignal that has been recorded on the optical disk 212 is reproduced bythe optical head 208, and amplified by the playback amplifier 213, anddigital data is restored by the demodulator 214 and decoder 215. Adigital video signal is then restored by the information expanding means217 adopting, for example, the MPEG decoding technique. An analog outputimage signal 219 or the like is produced by the D/A converter 218 andthen displayed on a monitor or the like.

Stored in the address memory 223 are, for example, the start addresseson the optical disk of the coded data representing selected images suchas images to be retrieved or the like, the start addresses of datacontaining information required for reproducing the coded data, i.e.,the start addresses of GOP headers of GOPs containing the coded data,and the start addresses of sequence headers of sequences containing theGOPs.

The contents of the address memory 223 are recorded into an imageinformation table set up on the optical disk 212 at, for example, auser's desired time instant by manipulating the switch 224.

The image information table thus set up on the optical disk 212 is usedto retrieve and display any selected image recorded on the optical disk212. The underlying idea has been described in conjunction withEmbodiment A1.

For retrieving and displaying a selected image, the recording/playbackdevice carries out the operations described below. When retrieval isstarted, access is then gained to the image information table set up onthe optical disk 212, and the start address of coded data representingthe selected image, the start address of a GOP header of a GOPcontaining the selected image, and the start address of a sequenceheader are stored.

Based on the start addresses, the sequence header is accessed in orderto acquire the sequence information. The GOP header is then accessed.Decoding is then started from the leading picture of the GOP. Afterdecoding of a picture of the selected image is completed, the selectedimage is displayed. The series of operations are illustrated in theflowchart of FIG. 3.

Embodiment A3

FIG. 4 is a block circuit diagram showing a video diskrecording/playback device of Embodiment A3. The reference numeralsidentical to those in FIG. 2 denote identical or corresponding parts. Itadditionally comprises an A/D converter 231 receiving an input imagesignal 230, an information compressing means 232, an address monitoringcircuit 234 receiving an image selection signal 235 indicating that animage has been selected, and associating coded data with an address onthe video disk 212, and a header detecting circuit 236 for detecting aGOP header and sequence header in the bit stream of coded data. A switch424 is provided for changing a signal to be recorded on the optical disk212 from the input image signal 230 to a signal representing thecontents of the address memory 223 or vice versa at, for example, auser's desired time instant.

Next, the operations will be described. The input image signal 2330having the GOP structure that has been described in conjunction withEmbodiment A1 is converted into a digital signal by the A/D converter231, and then transformed into an image information signal thatrepresents high-efficiency coded data by the information compressingmeans 232 adopting, for example, the MPEG technique that is now becomingan international standard for high-efficiency compression of motionpictures. At this time, a GOP header containing information required fordecoding each GOP is appended to the start of each GOP. A sequenceheader containing information concerning a sequence composed of aplurality of GOPs is appended to the start of the sequence.

The information is encoded so that it can be recorded on the opticaldisk 212. The encoded information is modulated on the disk in order tominimize influence of inter-code interference, and then recorded on theoptical disk 212 using a laser beam.

For playback, a compressed video signal recorded on the optical disk 212is reproduced by the optical head 208, and amplified by the playbackamplifier 213, and digital data is then restored by the demodulator 214and decoder 215. A digital video signal is then restored by theinformation expanding means 217 adopting, for example, the MPEG decodingtechnique. An analog output image signal 219 or the like is produced bythe D/A converter 218, and then displayed on the monitor or the like.

The aforesaid various headers contain "unique words" serving asinformation for identification. Various headers can be detected anddetermined by detecting the words. The header detecting circuit 236 usesthis procedure to detect a GOP header and sequence header.

Addresses for specifying locations are assigned in advance on theoptical disk 212. The address monitoring circuit 234 monitors theaddresses to determine at which address on the optical disk 212 codeddata representing an image is recorded.

Owing to the address monitoring circuit 234 and header detecting circuit236, the addresses at which the latest GOP header and sequence headerare recorded can be obtained. The addresses are stored in the addressmemory 223.

When a selected image, such as one to be retrieved is selected fromimages represented by the input image signal 230, the image selectionsignal 235 indicating that an image has been selected and a signal sentfrom the address monitoring circuit 234 are used to learn an address atwhich coded data representing the selected image is recorded. Theaddress is then stored in the address memory 223.

The addresses stored in the address memory 223 are recorded into theimage information table set up on the optical disk 212 by manipulatingthe switch 224 at a user's desired time instant.

Using the image information table set up on the optical disk 212 in thisway, any selected image can be retrieved from the optical disk 212 andthen displayed. The underlying idea has been described in detail inconjunction with Embodiment A1.

For retrieving and displaying a selected image, the recording/playbackdevice carries out the operations described below. When retrieval isstarted, access is then gained to the image information table set up onthe optical disk 212, and the start address of coded data representing aselected image, the address of a GOP header of a GOP containing theselected image, and the address of a sequence header are stored.

Based on the addresses, the sequence header is accessed in order toacquire sequence information. The GOP header is then accessed. Decodingis then performed starting with the leading picture of the GOP. Afterdecoding of the picture of the selected image is completed, the selectedimage is displayed. The series of operations is identical to the onedescribed in the flowchart of FIG. 3.

Embodiment A4

FIG. 5 is a block circuit diagram showing a video diskrecording/playback device of Embodiment A4. Reference numerals identicalto those in FIG. 4 denote identical or corresponding elements or parts.A header detecting circuit 241 of this embodiment is provided fordetecting a GOP header and sequence header in a bit stream of coded dataoutput from the decoder 215. A switch 224 is manipulated for recordingthe contents of the address memory 223 onto the optical disk 212 at auser's desired time instant.

Next, the operations will be described. High-efficiency coded datarepresenting an image having the GOP structure described in conjunctionwith Embodiment A1 is recorded on the optical disk 212. A GOP headercontaining information required for decoding each GOP is appended to thestart of each GOP. A sequence header containing information concerning asequence composed of a plurality of GOPs is appended to the start of thesequence.

For reproducing data from the optical disk 212, a compressed videosignal recorded on the optical disk 212 is reproduced by the opticalhead 208, and amplified by the playback amplifier 213, and digital datais then restored by the demodulator 214 and decoder 215. A digital videosignal is then restored by the information expanding means 217 adopting,for example, the MPEG decoding technique. An analog output image signal219 or the like is produced by the D/A converter 218, and then displayedon a monitor or the like.

The foregoing various headers contain "unique words" serving asinformation for identification. The various headers can be detected anddetermined by detecting the words. The header detecting circuit 241 usesthis procedure to detect a GOP header and sequence header.

Addresses for specifying locations are assigned in advance on theoptical disk 212. The address monitoring circuit 234 monitors theaddresses to determine at which address on the optical disk 212 codeddata representing an image is recorded.

Owing to the address monitoring circuit 234 and header detecting circuit241, addresses at which the latest GOP header and sequence header arerecorded can be obtained. The addresses are stored in the address memory223.

When a selected image to be retrieved is selected from imagesrepresented by the output image signal 219, the image selection signal235 indicating that an image has been selected and a signal provided bythe address monitoring circuit 234 are used to obtain an address atwhich coded data representing the selected image is recorded. Theaddress is then stored in the address memory 223.

The contents of the address memory 223 are recorded into the imageinformation table set up on the optical disk 212 at, for example, auser's desired time instant by manipulating the switch 224.

Using the image information table set up on the optical disk 212, anyselected image can be retrieved from the optical disk 212 and thendisplayed. The underlying idea has been described in conjunction withEmbodiment A1.

For retrieving and displaying a selected image, the recording/playbackdevice carries out the operations described below. When retrieval isstarted, access is then gained to the image information table set up onthe optical disk. 212, and the start address of coded data representingthe selected image, the address of a GOP header of a GOP containing theselected image, and the address of a sequence header are stored.

Based on the addresses, the sequence header is accessed in order toacquire sequence information. The GOP header is then accessed. Decodingis then performed starting with the leading picture of the GOP. Afterdecoding of the picture of the selected image is completed, the selectedimage is displayed. The series of operations is identical to the onedescribed in the flowchart of FIG. 3.

Embodiment A5

FIG. 6 is a block circuit diagram showing a video diskrecording/playback device of Embodiment A5. Reference numeral identicalto those in FIG. 5 denote identical or corresponding elements. A switch224 is be manipulated for recording the contents of the address memory223 onto the optical disk 212 at, for example, a user's desired timeinstant.

A switch 251 is provided for changing processing from normalreproduction to list display or vice versa. A low-pass filter (LPF) 253is provided for contracting (reducing the size of) the screen or pictureof expanded image data. A sub-sampling circuit 254 is provided toperform one-Nth sub-sampling so as to obtain the contracted image of1/N. A list image memory 255 is provided for storing a list displayscreen. A switch 252 is manipulated for displaying a list display imagerecorded on the list image memory 630.

Next, the operations will be described. High-efficiency coded datarepresenting an image having the GOP structure described in conjunctionwith Embodiment A1 is recorded on the optical disk 212. A GOP headercontaining information required for decoding each GOP is appended to thestart of each GOP. A sequence header containing information concerning asequence composed of a plurality of GOPs is appended to the start of thesequence.

For reproducing data from the optical disk 212, a compressed videosignal recorded on the optical disk 212 is reproduced by the opticalhead 208 and amplified by the playback amplifier 213, and digital datais then restored by the demodulator 214 and decoder 215. A digital videosignal is then restored by the information expanding means 217 adopting,for example, the MPEG decoding technique. An analog output image signal219 or the like is produced by the D/A converter 218 and then displayedon a monitor or the like.

Stored in the address memory 223 are the start addresses on the opticaldisk of coded data representing selected images such as images to beretrieved, the start addresses of data containing information requiredfor reproducing the coded data, the start addresses of GOP headers ofGOPs containing the coded data, and the start addresses of sequenceheaders concerning sequences containing the GOPs.

The contents of the address memory 223 are recorded into the imageinformation table set up on the optical disk 212 at, for example, auser's desired time instant by manipulating the switch 224.

Using the image information table set up on the optical disk 212, anyselected images recorded on the optical disk 212 can be displayed in theform of a list. Thus, the recorded contents of the optical disk 212 canbe learned promptly. For displaying selected images in the form of alist, the recording/playback device carries out the operations describedbelow. When list display is started, access is then gained to the imageinformation table set up on the optical video disk 212, and the startaddress of coded data representing a selected image, the address of aGOP header of a GOP containing the selected image, and the address of asequence header are stored.

Based on the addresses, the sequence header is accessed in order toacquire sequence information. The GOP header is then accessed. Decodingis then started with the leading picture of the GOP. After decoding ofthe picture of the selected image is completed, the switch ismanipulated to transform the selected image into a contracted image.This can be implemented by removing high-frequency components by meansof the low-pass filter 628, and performing one-Nth sub-sampling, bymeans of the sub-sampling circuit 629, so as to obtain the contractedimage of 1/N. The contracted image is stored in the list image memory255.

By repeating the foregoing series of operations, a list image composedof N contracted screens of selected images recorded on the disk isstored in the list image memory 255. The series of operations isillustrated in the flowchart of FIG. 7. FIG. 8 shows a list image storedin the list image memory. When the list image is displayed bymanipulating the switch 252, the contents of the optical disk 212 can belearned readily.

Embodiment A6

FIG. 9 shows a disk format of a video disk in accordance with EmbodimentA6. In FIG. 9, reference numeral 261 denotes a track. 262 denotes asector. 263 denotes a data area. 264 denotes a file management area inwhich basic data representing a disk type and others is recorded. 265denotes an image information table area.

Next, a coding scheme will be described using FIG. 1 showing the codingscheme employed in Embodiment A1. Reference numerals identical to thosein FIG. 1 denote the same components. A collection of a plurality ofinput images is referred to as a GOP (group of pictures). The GOPincludes an I picture 104 encoded within a frame, P pictures 105inter-frame encoded by forward motion compensation, and B pictures 106inter-frame encoded by forward and backward motion compensation. Inputimage information composed of a succession of GOPs is high-efficiencycoded. The GOP header 103 describing information required for decodingeach GOP is appended to the coded data representing each GOP. Acombination of GOPs is referred to as a sequence. The sequence header101 describing information representing, for example, a screen size ofthe pictures of the sequence may be appended to the start of thesequence. The coded data composed of these data items is recorded in thedata area 263 on the video disk on which addresses are assigned toareas.

For reproduction, the inverse of the foregoing recording procedure iscarried out. A video signal recorded on the video disk is thusreproduced and displayed.

Assuming that the B6 picture 106 is specified as a selected image suchas an image to be retrieved, the I1 picture 104 and P4 picture 105 mustbe decoded first, in order to decode the B6 picture 106. For decodingthe P4 picture 105, the I1 picture 104 must be decoded. Sinceinformation required for decoding the I1 picture 104 is described in theGOP header 103, the information residing in the GOP header 103 isnecessary. Normally, only one I picture resides in each GOP 102, and theI picture follows the GOP header 103. For displaying the B6 picture 106as a select screen, therefore, information concerning the GOP 102containing the B6 picture 106 should be read from the GOP header 103.The I1, B2, B3, . . . pictures are then decoded in that order, until theB6 picture 106 is decoded and then displayed. Therefore, the startaddress 109 on the disk in the area in which the coded data representingthe B6 picture 106 is recorded and the start address 108 of a GOP headerof the GOP 102 containing the B6 picture 106 is necessary. Sinceinformation in the sequence header 101, which is needed for decoding theB6 picture 106, may become necessary, the start address 107 of thesequence header is required in addition to the above addresses.

The address information is stored in, for example, a memory in therecording device, and then recorded into the image information tableresiding in the image information table area 265 on the video disk at,for example, a user's desired time instant. The image information tablethus recorded on the video disk is as shown in FIG. 1B.

For retrieving the B6 picture 106 from the video disk on which data isrecorded as mentioned above, the operations described below are carriedout. First, when a retrieval instruction is issued, access is gained tothe image information table set up on the disk. The start address 109 onthe disk at which coded data representing the B6 picture 106 isrecorded, the start address 108 of a GOP header of the GOP 102containing the B6 picture 106, and, if necessary, the start address 107of a sequence header are read from the image information table. A jumpis then made to the sequence header 101 and GOP header 103. Informationin the headers is then acquired. Decoding is performed sequentially,starting with the I1 picture 104. When decoding of the B6 picture 106 iscompleted, a decoded screen of the B6 picture 106 is displayed.Retrieval is then terminated.

In this example, the B6 picture 106 is specified as a selected image.Even when any other picture is selected, the aforesaid procedure isrepeated.

In the aforesaid embodiments, a selected image is an image to beretrieved. The inventive concepts described in connection with the aboveembodiments can apply to an image showing the start of a program or animage at which previous reproduction has been suspended.

Embodiment B1

FIG. 10 is a block diagram showing a video disk recording/playbackdevice of Embodiment B1. The reference numerals identical to those inFIG. 2 and FIG. 4 denote identical or corresponding parts. An ID signalgenerating circuit 302 generates ID signals for identifying the opticaldisk 212. An information table memory 304 stores the start addresses ofcoded data of the selected images such as the images to be retrieved,the start addresses of data containing information required for decodingthe coded data, and the ID signals output by the ID signal generatingcircuit 302. A switch 224 is for inputting the ID signal generated bythe ID signal generating circuit 302, on the optical disk 212 at auser's desired time instant.

The operations will next be described. Recorded on the optical disk 212are high-efficiency coded data having images of a GOP structure. Thestructure of the recorded coded data structure is as shown in FIG. 1A.Appended to the start of each GOP is a GOP header 103 containinginformation required for decoding the GOP. Appended to the start of asequence composed of a plurality of GOPs may be a sequence header 101containing information concerning the sequence.

For reproducing from the optical disk 212, the compressed video signalrecorded on the optical disk 212 is reproduced by the optical head 208,amplified by the playback amplifier 213, and digital data is restored bythe demodulator 214 and the decoder 215. A digital video signal is thenrestored by an information expanding means 217 adopting the MPEGdecoding method, for example, and an analog output image signal 219 orthe like is obtained by the D/A converter 218, and is displayed on themonitor or the like.

Stored in the information table memory 304 are the ID signal generatedby the ID signal generating circuit 302 for identifying the optical disk212, and the start address of data containing information required forreproducing the coded data, i.e., the start address of the GOP headercontaining the coded data, the start address of the sequence headerconcerning the sequence containing the GOP and the like header. Dataconcerning selected images of a plurality of optical disks may also bestored. In this case, the ID signals of the data are different.

The table stored in the information table memory is schematically shownin FIG. 11B.

The ID signal generated by the ID signal generating circuit 302 isrecorded in a specific area on the optical disk 212, by manipulating theswitch 224 at the user's desired instance.

By utilizing the ID signal recorded in the specific area of the opticaldisk 212, and the information table memory 304, any selected image onthe optical disk 212 may be retrieved and displayed. The reason will bedescribed in detail with reference to FIG. 1A and FIG. 11.

FIG. 11 is a schematic representation of the table recorded in theinformation table memory 304 in the device. The reference numeralsidentical to those in FIG. 1B denote identical or corresponding parts.Reference numeral 114 denotes a column in which ID signals foridentifying the video disk 212 are written.

The structure of the GOP, and the operations during retrieval and fastplayback are identical to those described with reference to EmbodimentA1, except as described below. That is, ID signals for identifying theoptical disks 212 are also stored in the information table memory 304.

The ID signal is recorded in the specific area on the optical disk 212by manipulating the switch 224 at a user's desired time instance.

Data concerning the different ID signals may also be stored in theinformation table memory 304.

By means of the video disk recording/playback device configured asdescribed above, any selected image can be retrieved and displayed,depending on the individual optical disk. This is implemented throughoperations illustrated in the flowchart of FIG. 12.

When retrieval operation is started by input of a retrieval command bythe user, the ID signal recorded in the specific area on the opticaldisk 212 is read (step S1). The sequence header address, the GOP headeraddress, the selected image start address and the like are read from theinformation table memory 304 in the device (step S2), and a jump is madeto the sequence header and the GOP header, and information writtentherein is obtained (step S3, step S4). Decoding is made starting withthe picture at the start of the GOP (step S5). When the decoding of theselected image is completed (step S6), the decoded screen of theselected image is displayed (step S7). The steps S3 to S7 are repeateduntil the retrieval termination command is found to have been issued atthe step S8.

Embodiment B2

FIG. 13 is a block circuit diagram showing a video diskrecording/playback device of Embodiment B2. Reference numerals identicalto those in FIG. 4 and FIG. 10 denote identical or corresponding parts.An image selection signal 235 indicates that the selected image such asthe image to be retrieved has been selected.

The difference of this embodiment from Embodiment B1 will next bedescribed. The input image signal 230 having the GOP structure describedabove is converted at the A/D converter 231 into a digital signal, andis converted at the information compression means 232 into ahigh-efficiency coded image information signal. During such time, a GOPheader containing information required for decoding the GOP is appendedto the start of each GOP, and a sequence header containing informationconcerning the sequence is appended to the start of the sequenceconsisting of a plurality of GOPs.

The image information is then encoded for recording on the optical disk212, and modulated so as to reduce the effects of inter-codeinterferences on the optical disk, and is then recorded on the opticaldisk 212, using a laser.

The GOP header and sequence header contain a "unique word" which isinformation for identifying them, and the header detecting circuit 236detects the unique word to detect and judge each header.

The address monitoring circuit 234 monitors which address on the opticaldisk 212 the coded data corresponding to the image is recorded, and itis possible to know the address where the latest GOP header and sequenceheader are recorded, on the basis of the address monitored by theaddress monitoring circuit 234 and the header detected by the headerdetecting circuit 236. The address is stored in the information tablememory 304.

When the selected image is selected from among the input image signal230, the address at which the coded data corresponding to the selectedimage is recorded is known, by using the image selection signal 235indicating that this image has been selected, and the signal from theaddress monitoring circuit 234. This address is stored in theinformation table memory 304.

The ID signal generating circuit 302 generates an ID signal foridentifying the optical disk 212, and stores the ID signal in theinformation table memory 304. A schematic drawing of the table is givenin FIG. 11.

The ID signal is recorded in a specific part on the optical disk 212, bymanipulating the switch 224 at a user's desired time instant, forexample.

By using the ID signal recorded on the optical disk 212, and the addressof the selected image stored in the information table memory 304 withinthe device, arbitrary selected image can be retrieved and displayed in aprocedure similar to that described in connection with Embodiment B1.

The operations for retrieving and displaying the selected image aresimilar to that shown in FIG. 12, and their description is omitted.

Embodiment B3

FIG. 14 is a block circuit diagram showing a video diskrecording/playback device of Embodiment B3. Reference numerals identicalto those in FIG. 13 denote identical or corresponding parts. Adifference from Embodiment B2 is that a header detecting circuit 241 ofthis embodiment detects GOP headers and sequence headers in the bitstream of the coded data reproduced from the optical disk 212.

The operations of this embodiment will be described with regard to theaspects different from those of Embodiment B2.

The header detecting circuit 241 detects the GOP headers and sequenceheaders in the image data decoded by the decoder 215, and the addressmonitoring circuit 234 monitors at which address on the optical disk 212the coded data corresponding to the image is recorded.

By utilizing the address monitoring circuit 234 and the header detectingcircuit 236, it is possible to know the address where the latest GOPheader and sequence header are recorded, and this address is stored inthe information table memory 304.

When a desired image is selected from among the output image signals219, the image selection signal 235 indicating that the image has beenselected is input to the address monitoring circuit 234, and it ispossible to know the address where the coded data of the selected imageis recorded, and this address is stored in the information table memory304.

The table thus stored in the information table memory 304 is asillustrated in FIG. 11.

The above-mentioned ID signal is recorded in a specific part of theoptical disk 212 by manipulating the switch 224 at a user's desired timeinstant, for example.

By utilizing the ID signal recorded in the optical disk 212 and theaddress of the selected image stored in the information table memory 304in the device, it is possible to retrieve and display any selected imagefrom the optical disk 212, by the procedure similar to that described inconnection with Embodiment B1.

The operations for retrieving and displaying the selected image aresimilar to those of the flowchart of FIG. 12, and their description willbe omitted.

Embodiment B4

FIG. 15 is a block circuit diagram showing a video diskrecording/playback device of Embodiment B4. Reference numerals identicalto those in FIG. 6 and FIG. 10 denote identical or corresponding parts.

The operations of the parts different from Embodiment B1 will next bedescribed. The operations during recording are identical to those ofEmbodiment B1.

During playback, the ID signal recorded in the optical disk 212 and theinformation table memory 304 in the device are utilized for list displayof any selected image recorded in the optical disk 212, and the contentsof recording on the optical disk 212 can be known promptly.

The operations for list display of the selected image will next bedescribed with reference to the flowchart of FIG. 16.

When the list display is commanded, and the list display operation isstarted, and the operations similar to those from the steps S1 to S6described with reference to FIG. 12 are performed. Then, at the stepS11, the switch 251 is switched to the side of the LPF 253, so that thehigh-frequency components are removed in preparation for the subsequentprocessing. Then, subsampling to 1/N is conducted at the sub-samplingcircuit 254, for conversion into contracted image of 1/N. The contractedimage is then stored in the list image memory 255 (step S12).

By repeating the above described sequence of operations (step S12), alist image formed of contracted screens of N selected images recorded inthe disk, in the list image memory 255. By manipulating the switch 252at the step S14, the list image stored in the list image memory 255 canbe displayed as shown in FIG. 8, and the contents recorded on theoptical disk 212 can be readily known.

Embodiment B5

FIG. 17 is a block circuit diagram showing a video disk playback deviceof Embodiment B5. Reference numerals identical to those in FIG. 10denote identical or corresponding parts. An ID signal detecting circuit306 is provided for detecting and utilizing the bit sequence of imagesignal or the like recorded in the specific part on the optical disk212, and generating an ID signal. A switch 308 is switched betweennormal playback and generation of an ID signal from the bit sequencefrom the specific part on the video disk 212.

The operations of Embodiment B5 will next be described with regard tothe parts different from those during playback of Embodiment B1. Becausethe image signal and the like recorded on each optical disk isdifferent, the bit sequence recorded in the specific part of the opticaldisk is different from one disk to another. The ID signal detectingcircuit 306 generates an ID signal for identifying the optical disk fromthe bit sequence of the image signal or the like recorded in thespecific part of the optical disk.

The operations for retrieving and display any selected image from theimages recorded in the individual optical disks will next be described.

FIG. 18 is a flowchart showing the operation. When the retrieval iscommanded, the switch 308 is switched to the side of the ID signaldetecting circuit 306 at the step S21. The ID signal detecting circuit306 detects and utilizes the bit sequence recorded in the specific partof the optical disk 212 to generate an ID signal. At the step S2, thesequence header address, the GOP header address, the selected imagestart address and the like corresponding to the ID signal generated atthe step S21 are read from the information table memory 304 in thedevice, and at the step S3 the sequence header is accessed, and at thestep S4 the GOP header is accessed, and the information written there isobtained. At the step S5, the switch 308 is switched to the side of theinformation expanding means 217, and decoding is started from the startpicture in the GOP, and when the decoding of the selected images is overat the step S6, the decoded screen of the selected images is displayedat the step S7, and the step S3 to step S7 are repeated and when it isfound, at the step S8, that the retrieval is over, the operation isterminated.

Embodiment B6

FIG. 19 is a block circuit diagram showing a video disk playback deviceof Embodiment B6. Reference numerals identical to those in FIG. 13 andFIG. 17 denote identical or corresponding parts.

The operations of Embodiment B6 will next be described with regard tothe parts different from those during playback of Embodiment B1. Thevarious headers described above contain a "unique word" which isinformation for identifying them. By detecting the unique word, eachheader is detected and identified. The header detecting circuit 241utilizes this method to detect the GOP header and the sequence header.

The addresses are allocated for specifying the locations on the opticaldisk 212, and the address monitoring circuit 234 monitors whichaddresses on the optical disk the coded data corresponding to the imageis recorded in.

Utilizing the address monitoring circuit 234 and the header detectingcircuit 241, it is possible to know the address where the latest GOPheader and sequence header are recorded, and the address is stored inthe information table memory 304.

When the selected image is selected from among the output image signals219, the address where the coded data of the selected image is recordedcan be known from an image selection signal 235 indicating that theimage has been selected, and the signal from the address monitoringcircuit 234, and the address is stored in the information table memory304.

When the switch 308 is manipulated, the ID signal detecting circuit 306generates an ID signal for identifying the optical disk 212, from thebit sequence recorded in the specific part of the optical disk 212, andthis ID signal is also stored in the information table memory 304.

In this way, the table stored in the information table memory isschematically shown in FIG. 11.

When the video disk playback device having the configuration describedabove is utilized for retrieving and displaying an arbitrary selectedimage recorded on the optical disk 212, the following operations areperformed. When retrieval is started, the switch 308 is manipulated, andthe bit sequence recorded in the specific part of the optical disk 212is detected, and the ID signal is then generated using the detected bitsequence. The sequence header address, GOP header address, selectedimage start address and the like corresponding to the generated IDsignal is read from the information table memory 304 in the device, andJump is made to the sequence header and the GOP header, and theinformation written there is obtained. Then, decoding is started at thestart picture of the GOP, and when the decoding of the selected image iscompleted, the decoded screen of the selected image is displayed. Theflowchart for this sequence of operations is similar to that of FIG. 18.

Embodiment B7

FIG. 20 is a block circuit diagram showing a video diskrecording/playback device of Embodiment B7. Reference numerals identicalto those in FIG. 15 and FIG. 17 denote identical or corresponding parts.

The operations will next be described. High-efficiency coded data of theimage having a GOP structure is described in the optical disk 212.Appended to the start of each GOP is a GOP header containing informationrequired for decoding the GOP. A sequence header containing informationconcerning the sequence may be appended to the start of the sequenceconsisting of a plurality of GOPs.

To reproduce the optical disk 212, the compressed image signal recordedin the optical disk 212 is amplified at the playback amplifier 213, anddecoded by the demodulator 214 and the decoder 215 into digital data.Then, the information expanding means 217, for instance, decodes thedigital image signal, and by means of the D/A converter 218 an analogoutput image signal 219 or the like is obtained, and displayed by amonitor or the like.

The image signal or the like recorded in each optical disk differs fromone disk to another, so that the bit sequence recorded in the specificpart of the optical disk differs from one disk to another. Utilizingthis fact, the ID signal detecting circuit 306 generates an ID signalfor identifying the optical disk 212, from the bit sequence of the imagesignal or the like recorded in the specific part.

Stored in the information table memory 304 are an ID signal generated bythe ID signal detecting circuit 306 for identifying the optical disk212, the start address on the disk of the coded data of the selectedimage, such as the image to be retrieved, on the optical disk 212, andthe start address of the data containing information required forreproducing the coded data, i.e., the start address of the GOP header ofthe GOP containing the coded data and the start address of the sequenceheader concerning the sequence containing the GOP and the like.

Data concerning the selected image on an optical disk different from theoptical disk 212 may also be stored in the information table. In such acase, the ID signal of the data differs depending on the optical disk212.

The table thus stored in the information table memory is schematicallyshown in FIG. 11.

By utilizing these, any selected images recorded in the optical disk 212can be list-displayed, and the contents of recording in the optical disk212 may be known promptly. The operation for the list display of theselected images is shown by the flowchart of FIG. 21.

First, the list display operation is started. When the user manipulatesthe switch 308, then at the step S31, the ID signal detecting circuit306 generates an ID signal utilizing the bit sequence recorded in thespecific part of the optical disk 212. At the step S2, the sequenceheader address, GOP address, the selected image start address and thelike corresponding to the ID signal generated at the step S31 are readfrom the information table memory 304 in the device.

On the basis of these, at the step S3, the sequence header is accessedto obtain the sequence information, and the step S4, the GOP header isaccessed. At the step S5, the decoding is started from the picture atthe start of the GOP, and at the step S6, after decoding of the pictureof the selected image is completed, the switch 251 is manipulated, andat the step S11, a processing for conversion into contracted images isapplied. For this purpose, high-frequency components are removed by thelow-pass filter 253 for the subsequent processing. After that,contracted images of 1/N are obtained by 1/N sub-sampling by means ofthe sub-sampling circuit 254. The resultant contracted images are storedin the list image memory 255.

By repeating the sequence of operations, the list image memory 255stores the list image formed of contracted images of the N selectedscreens recorded in the disk (step S13). A list image stored in the listimage memory is as shown in FIG. 8. At the step S14, the switch 252 ismanipulated and the list image is displayed, and the contents recordedin the optical disk 212 can be readily known.

In above description of each of the embodiments, the selected images aremainly assumed to be images to be retrieved. However, the inventiveconcepts described in connection with the above embodiments can beapplied to images for head-of-program finding, images at which theinterruption took place in the preceding playback, and the like.

Embodiment C1

FIG. 22 is a block diagram showing the configuration of an optical diskrecording/playback device of Embodiment C1. FIG. 23 is a sector mapdiagram showing the data arrangement on the optical disk according toEmbodiment C1.

As illustrated in FIG. 22, the optical disk recording/playback device ofthis embodiment comprises an A/D converter 401, a coding means 402, aGOP file forming means 403, a GOP information detecting means 404, a GOPfile sequence table (GST) data forming means 405, a GOP informationtable data forming means 406, a write control means 407, a data blockconfiguring means 408, a modulator 409, a laser drive circuit 410, anoptical head control means 411, and an optical head 412 for writing dataon or reading data from an optical disk 413. The optical diskrecording/playback device further comprises a sequence identifyingsignal input means 414, a time position identifying signal input means415, a playback amplifier 416, a demodulator 417, an error correctingmeans 418, a GOP file sequence table (GST) data detecting means 419, aGOP information table data detecting means 420, a read control means421, a GOP continuation means 422, a decoding means 423, and a D/Aconverter 424.

In FIG. 23, reference numeral 431 denotes a boot sector for storing aboot code, 432 denotes a GOP file sequence table (GST) region forstoring information concerning the arrangement of the GOP files (to bedescribed later), 433 denotes GOP information region, and 434 denotesuser region.

In the present embodiment, the sector addresses are arranged in theascending order from the inside of the disk, and the optical disk is forrecording image signals obtained by compression coding by MPEG method.The image data coding method according to the MPEG method does notnecessarily require a sequence header (SH) at the start of each GOP. Inthis example, it is assumed that no sequence header is appended to theGOP3. It is also assumed that GOP is recorded by variable-data rate, aswas described above. Identical reference numerals denote identical orcorresponding parts.

The operations during recording will next be described. The input imagesignal is input to and converted to a digital image signal at the A/Dconverter 401, and is then coded at the coding means 402 by the MPEGmethod, to be data-compressed. The coding by the MPEG method is madetaking each GOP as a unit, each GOP consisting of image signal for apredefined number of frames. The coded image signal has a layeredstructure as shown in FIG. 41. The sequence layer, which is theupper-most layer, is configured of GOPs (some of which have a SH, whileother do not, as described above), and each GOP contains, at the startthereof, a GOP start code, not indicated.

The GOP file forming means 403 detects the GOP start code contained ineach GOP, and thereby separates each GOP. It also detects the sequencestart code in the SH for each GOP. It also forms a GOP file, which is adata file, from one GOP that has been separated. The GOP file is inputto the data block configuring means 408, and to the GOP informationdetecting means 404. The GOP file forming means 403 forms a GOP starttiming signal in accordance with the detected GOP start codes, and inputit to the write control means 407.

The sequence identifying signal is supplied from the sequenceidentifying signal input means 414, for inputting the sequenceidentifying signal, to the write control means 407, and a sequence startsector address indicating the sector from which the data for each sectoris to be recorded. In accordance with the sequence start sector addressand the GOP start timing signal, a GOP start sector address indicatingthe sector from which each GOP file is to be recorded. Here, it isassumed that GOP file is recorded in sectors of addresses consecutivefrom the sequence start sector address. The situation where vacantsectors on the disk which permit recording will be described later. Itis also assumed that the No. 1, No. 2, . . . , indicate the contents ofthe sequence identifying signals.

The GOP having been coded by the MPEG method at the coding means 402has, at the start thereof, data (time code) indicating the time from thestarting time instant of the sequence to which the GOP belongs. The GOPinformation detecting means 404 detects the information concerning theGOP, such as the time code, from the GOP in each input GOP file, andalso detects the file size, the coding rate, and the like, from theinput GOP file.

The GST data forming means 405 forms, for each sequence (title, program)shown in FIG. 25, GST table data storing the sector addresses fordetermining the order of playback of the GOP files of each GOP formingthe sequence, from the sequence identifying signal input from the writecontrol signal and the GOP start sector address formed for each GOP, andoutput it to the data block configuring means 408.

The GOP information table data forming means 406 generates, for each GOPfile, a file name, and generates GOP information table data, shown forexample in FIG. 24, for each file name, in accordance with the GOP startsector address for each GOP input from the write control means, the timecode indicative of the time from the start of the sequence, detected bythe GOP information table data forming means 406, the size of the GOPand the coding rate, and outputs it to them to the data blockconfiguring means 408. The file name of each GOP is capable ofidentifying the sequence to which the GOP belongs.

The data block configuring means 408 performs processing, such asappending error correction codes to the input GOP file, and configures,for each GOP file, a data block (hereinafter referred to as a GOP filedata block) of a predefined format. An end detecting identifying code isprovided at the end of each GOP file data block.

Similarly, the data block configuring means 408 configures, from theinput GST data and GOP information table data, data blocks (hereinafterreferred to as GST data block and GOP information table data block,respectively).

The GOP file data block is subjected to a predefined modulation at themodulator 409, and sent to the laser drive circuit 410, from which alaser modulated in accordance with the modulated signal is output, andapplied via the optical head 412 to the optical disk 413 for recording.

The recording is made such that each Each GOP file data block isrecorded in the user region 434 in the sector map shown in FIG. 23, suchthat each GOP file is arranged from the start of the sector.

In the same way as the GOP file data block, the data of the GST datablock and GOP information table data block are also modulated by themodulator 409, and recorded on the optical disk 413 by means of theoptical head 412. They are recorded in the sectors in the GST region 432and GOP information region 433 in the sector map shown in FIG. 23.

The write control means 407 manages the sector addresses in which theGOP files, GST data and GOP information table data are recorded. Thatis, the sector address (hereinafter referred to as GOP recording sectoraddress) for recording each GOP file is generated by sequentialincrement, starting with the GOP start sector address generated asdescribed above. Each time the GOP file data is over, sequentialincrement starting with the next GOP start sector address is conducted,to generate the GOP recording sector address. The GOP recording sectoraddresses thus generated are input to the optical head control means411.

The optical head control means 411 performs control such that access onthe optical disk 412 is conducted to the sector on the optical diskaccording to the GOP recording sector address, while tracking ismaintained.

In this way, each GOP file data block is recorded, such that each GOPfile is arranged from the starting part of the GOP start sectoraddresses.

Similarly, the write control means 407 generates recording sectoraddresses for recording the GST data and GOP information table data inaccordance with the sector address corresponding to the sector at thestart of the GST region and the sector address corresponding to thestart of the GOP information region 433. The GOP recording sectoraddresses thus generated are input to the optical head control means411, which performs control such that access is made to the sector onthe optical disk corresponding to the recording sector address.

In this way, GST data blocks and the GOP information table data blocksare recorded in the sectors in the GST region 432 and GOP informationregion 433.

As was described above, one GOP (with or without a sequence header) istreated as one GOP file, and each GOP file is recorded starting from thethe start of the sector of the sector indicated by the GOP start sectoraddress in the user region 434, as shown in FIG. 23. For instance, SH1and GOP1 are recorded as one GOP file 1 from the start of the sector ofthe sector address n. Even if the data of the GOP file 1 ends in themiddle of a sector (the sector of the sector address (n+5), in theillustrated example), SH2 and GOP2, which follow, are recorded as oneGOP file 2 from the start of the sector of the next sector address(n+6). Similarly, the GOP3 is recorded as one GOP file from the start ofthe sector of the sector address (n+10), and SH4 and GOP4 are recordedas one GOP file from the start of the sector of the sector address(n+18). Subsequent GOP files are similarly recorded in sequence.

The GOP start sector addresses of the GOP1 file, GOP2 file, GOP3 fileand GOP4 file are n, (n+5), (n+10) and (n+18), respectively.

GOP file sequence table (GST) data for storing the data determining theorder of playback of the GOP files of the respective GOPs forming eachsequence, for each sequence (title, program), is recorded in the GOPfile sequence table (GST) recording region 32 shown in FIG. 23, asdescribed above. FIG. 25 shows the configuration of the GST datarecorded in the GST recording region 432. With regard to the GST data inthe drawing, the GOP files forming the sequence with a sequence name No.1, for example (title names and program names), are successivelyrecorded, with the GOP start sector addresses being the sectors of theaddress 1, address 2, address 3, address 4, . . .

For playing back the sequence with the sequence title No. 1 (title), theGOP files forming the sequence should be successively read, from thesectors, taking address 1, address 2, address 3, address 4, . . . as theGOP start sector addresses, and reproduced.

The GOP information table data storing, for each GOP file, the file nameindicating the GOP, the time from the start of the sequence of the GOP,the start sector address, file size, the coding rate, and otherattribute data is recorded in the GOP information region 433 shown inFIG. 23. FIG. 24 shows the table data recorded in the GOP informationregion 433. For instance, for the GOP file for the GOP1, i.e., the filewith the file name "GOP1", the time from the start of the sequence is"00:12:00", the sector address at which the GOP is started (GOP startsector address) is "500000" and the file size is "300000" and the codingrate is "4.5". Similarly, for GOP2, GOP3, GOP3 and the like, the filename indicating the GOP, the time from the start of the sequence of theGOP, the start sector address, the file size, the coding rate and otherattribute data are recorded in the GOP information region 433.

The operations for the normal playback will next be described. To readGST data, the read control means 421 generates the read sector address,and controls the optical head 412 via the optical head control means 411such that the optical head 412 accesses the GST recording region 432 onthe optical disk 413 shown in FIG. 23. The GST data block read from theGST recording region 432 is amplified by the playback amplifier 416, andsent to the error correction means 418, where processings such as errordetection by means of the error detection codes appended to the GST datablock is performed, and the resultant data is sent to the GST datadetection means 419.

Similarly, the GOP information table data recorded in the GOPinformation region 433 on the optical disk 412 is read, and sent to theGOP information table data detecting means 420.

The GST data and the GOP information table data having been read arestored in the GST data detecting means 419 and the GOP information tabledata detecting means 420.

The above operations are performed immediately after the optical disk413 is set in the device, or immediately after the recording andplayback operations are started.

The sequence identifying signal for identifying the sequence is suppliedfrom the sequence identifying signal input means 14 to the GST datadetecting means 420, which refers to the stored GST data to identify thestart sector address of each GOP file indicating the order of playbackof the GOP files corresponding to the sequence identifying signal.

For instance, where the GST data shown in FIG. 25 is read and stored,and the content of the sequence identifying signal is "No. 1", it isfound that the GOP files forming the sequence are successively recordedin the sectors, taking the address 1, address 2, address 3, address 4,as start sector addresses, and the start sector addresses of the GOPfiles having been identified are output to the read control means 421.

The read control means 421 generates GOP read sector addresses throughsequential increment from address 1 which is the start sector address ofthe GOP file played back first, from among the input start sectoraddresses.

When the end is detected by the end detection signal of the data blockof the GOP file input from the error correction means 418, GOP playbacksector addresses are next generated through sequential increment fromthe start sector address of the GOP file played back next.

The GOP read sector addresses thus generated are successively sent tothe optical head control means 411, to cause the optical head to accessthe sector of the GOP read sector address.

If the GOP files are successively recorded in consecutive sectors in theorder of playback, GOP files can be successively read, during playback,by identifying the sequence start sector address without referring theGST data, and making a Jump to the start of the next sector, as shown inFIG. 26 when one GOP file is over.

The GOP file data blocks successively read by the optical head 412 fromthe sectors in the user's region 434 are amplified by the playbackamplifier 416, and demodulated by the demodulator 417, and input to theerror correction means 418. The error correction means 418 performserror correction and the like, and the resultant data is input as theGOP file data to the GOP continuation means 422. The error correctionmeans 418 also detects the end identifying signal for detecting the endof the GOP file data block and supplies it to the read control means421.

The GOP continuation means 422 receives the GOP files in the separatedstate, and restores the GOP data in the bit stream (serial transmitsignal) state, in the continuous form and having a predefined structurecoded by the MPEG method shown in FIG. 8, and supplies it to thedecoding means 423. The continuous GOP data is expanded and decoded bythe decoding means 423 to become a digital image signal, and isconverted by the D/A converter 424 into an analog signal, and is outputas an output image signal.

Playback of a GOP positioned in the middle of a sequence (title,program) will next be described. In the same way as normal playbackdescribed above, it is assumed that the start sector address of each GOPfile indicating the order of playback of the GOP files corresponding tothe sequence to be played back is identified and the GOP filecorresponding to the GOP positioned in the middle of the sequence is theGOP file 2 in FIG. 23.

The read control means 421 sends the start sector address of the GOPfile 2 which is the GOP file corresponding to the GOP positioned in themiddle of the sequence to the optical head control means 411, and causesthe optical head 412 to access the sector of the start sector address(n+6). In the same way as the normal playback, the sectors aresuccessively accessed from the sector of the start sector address (n+6),and GOP file data blocks read from the sectors are supplied via theplayback amplifier 416, the demodulator 417, the error correction means418 to the GOP continuation means 422, as the GOP file data.

The GOP continuation means 422 receives the GOP file 2 having beenrecorded in the sector addresses (n+6) to (n+9) in the separated state,and restores GOP data in the form of a continuous bit stream (serialtransmit signal), and having a predefined structure coded by the MPEGmethod shown in FIG. 8, and supplies it to the decoding means 423. Sincethe GOP file 2 is recorded from the start of the sector of the sectoraddress (n+6) accessed first, it is ensured that data of the immediatelypreceding GOP1 will not be read first. For this reason, the GOP data canbe restored from the data read first, decoded by the decoding means 423,converted at the D/A converter 424 into an analog signal, and output asthe output image signal.

In this way, when a GOP positioned in the middle of a sequence (title,program) is played back, the sector accessed first does not contain anypart of the preceding GOP, and it is thus ensured that part of thepreceding GOP is not read from the sector accessed first, and the GOPcan be read from the start of the accessed sector, so that the timerequired for playing back the image signal and displaying the picturecan be shortened.

Editing, such as overwriting and tag recording, taking each GOP as aunit, will next be described. As was described, the recording statebefore the editing is such that each GOP is recorded from the start ofthe sector, as shown in FIG. 23. Description will be made of thesituation where GOP files of GOP3 and subsequent GOP files areoverwritten by new GOP files. In such a case, new GOP files, such asGOP3', GOP4', . . . are successively recorded from the start of thesector of the sector address (n+10) from which GOP3 is recorded, asshown in FIG. 27.

In the disk having been overwritten, the GOP2 having been recorded isnot affected by the overwriting, since it is maintained in the statebefore the editing, so that during reproduction through the edit point,failure of playback of GOP2 which is the GOP before the editing, oroccurrence of unnatural images can be avoided.

Recording on a media of a write-once type, in vacant sectors whichpermit recording and which are distributed over the disk, and playbacktherefrom will next be described. In the same way as the normalplayback, vacant sectors are identified by the GOP information tabledata detecting means 420, from the start sector address and file size ofthe respective GOP files in the GOP information table data read from theGOP information region 433 on the disk, and the sector addresses of thevacant sectors are supplied to the write control means 407.

The write control means 407 finds the vacant sector region where the GOPfiles of the sequence to be tag-recorded, from the file size extractedby the GOP information detecting means 404, and controls the access ofthe optical head 412 in the same way as in recording, such that the GOPfiles of the sequence to be tag-recorded are recorded in the consecutivevacant sector region, consecutively from the start of the sector.

In accordance with the sequence to be additionally recorded as shown inFIG. 25, the GST data generating means 405 additionally generates GSTsindicating the start sector addresses of the GOP files forming therespective sequences. The GOP information table data forming means 406generates table data consisting of GOP file names to be recorded andinformation concerning them. The table data is recorded in the GSTregion 432 and GOP information region 433 on the optical disk 413.

When the sequence recorded in sectors distributed over the disk are tobe reproduced, for instance in a situation where the GOP file of thesequence No. 2 is recorded in sectors being distributed over the user'sregion 434, during reproduction, by reading and referring to the GST,from the start sector addresses indicating the order of playback of thesequence No. 2, it is possible to identify the order of playback of thedistributed GOP files.

In the same way as the normal playback described above, the read controlmeans 421 generates GOP read sector addresses by sequential incrementfrom address A which is the start sector address of the GOP filereproduced first, from among the input start sector addresses.

When the end of the data block of the GOP file is detected, the GOP isdetected, the GOP playback sector addresses are generated throughsequential increment from the start sector address B of the GOP file tobe reproduced next.

The GOP read sector addresses thus generated are successively sent tothe optical head control means 11, and the optical head 412 is made toaccess the sector of the GOP read sector address, and the read data isdecoded to produce an image signal, which is then output.

Recording, taking each GOP file as a unit, can thus be made in thevacant sectors distributed over the disk, and the vacant sectors canthus be utilized effectively.

Playback of a GOP positioned at a desired time instant from the start ofa certain sequence (title, program) will next be described. First,sequence identifying signal for identifying the sequence and the timeposition identifying signal indicating the desired time instant to bereproduced are supplied from the sequence identifying signal input means414 and the time position identifying signal input means 415 to the GOPinformation table data detecting means 420.

In the same way as was described above, the GST data and GOP informationtable data are read from the GST region 432 and the GOP region 433, andsent to and stored in the GST data detecting means 427 and the GOPinformation table data detecting means 420. As shown in FIG. 24, the GOPinformation table data stores the time from the sequence startcorresponding to the file name of each GOP, the start sector address,size, coding rate, and the like of the GOP file. The file name isrecorded for identification of the sequence to which the GOP belongs.

When, for instance, the contents of the sequence identifying signal isNo. 1, and and the GOP at a time instant 00 min. 13 sec. 00 from thestart of the sequence is to be reproduced, the GOP information tabledata detecting means 420 refers to the GOP information table data storedin advance, and identifies the GOP file group which belong to thesequence indicated by the content No. 1 of the sequence identifyingsignal from the GOP file name. By referring to the time from thesequence start corresponding to the GOP file group of the GOPinformation table data, the GOP file whose file name is "GOP3" isidentified as the GOP file of which the time from the start of thesequence is 00 min. 13 sec. 00, and the start sector address is found tobe "500580". In this way, the GOP file at a desired time instant fromthe start of the sequence is identified, and the start sector address ofthe GOP file is identified (retrieve). The start sector address havingthus been identified (retrieved) is output to the GST data detectingmeans 419.

The GST data detecting means 419 refers to the GST data stored inadvance, and successively outputs the start sector address from thestart sector address of the GOP file specified by the GOP informationtable data detecting means 20, to the read control means 421.

The GOP read sector addresses are thereafter generated, in the same wayas the normal playback described above, through sequential incrementfrom the GOP start sector address supplied from the GOP file datadetecting means 420, until one GOP is over.

When the end of the data block of the GOP file is detected, the GOPplayback sector addresses are then generated through sequentialincrement of the start sector address of the GOP file to be reproducednext. In this way, the subsequent GOP read sector addresses aregenerated.

The generated sector addresses are input to the optical head controlmeans 411, and the optical head 412 is made to access the sector of theinput sector address, and the data is read. The data having been read ispassed through the playback amplifier 416, the decoder 417, the errorcorrection means 418 and the GOP continuation means 422, and decoded atthe decoding means 423, and output via the D/A converter 424, as theoutput image signal.

As was described above, the GOP data is recorded from the start of thesector, so that it is not necessary to search for the GOP identifiedwithin the sector, and it is sufficient if the reproduction is madesuccessively from the GOP recorded at the start of the sector of the GOPfile start sector address.

As has been described, when it is desired to reproduced from a GOP at adesired time from the start of a certain sequence (title, program), itis possible to readily and promptly identify the sector in which thedesired GOP is recorded. It is not necessary to search for the GOPhaving been identified in the sector, and is possible to shorten thetime until the desired image signal is reproduced.

In the above description, the MPEG method is used as the method forcompression coding of the image signal. The inventive concepts describedin connection with the above embodiments is applicable to any othercompression coding method in which a predefined number of images aretaken as a unit of coding.

The file name of the GOP file of the GOP information table data has beendescribed as one capable of identifying the sequence to which thecorresponding GOP belongs. But the arrangement may be such that, foreach file name, data permitting identification of the sequence to whichthe corresponding GOP belongs is disposed in the GOP information table.

In the above description, the GOP information table data includes thetime from the start of the sequence as information indicating theposition of the GOP in the sequence (title, program). However, otherinformation, such as information indicating the number of the GOP ascounted from the start of the sequence may be used. In such a case, thearrangement may be such that a signal indicating the number of the GOPas counted from the start of the sequence is input, and the GOP issearch for, and reproduced.

Embodiment D1

FIG. 28 schematically shows the configuration of a recording system inan optical disk recording/playback device of Embodiment D1.

As illustrated, the optical disk recording/playback device of EmbodimentD1 comprises an input terminal 501 through which an analog video signalis received, an A/D conversion means 502 for sampling an input analogvideo signal at a certain frame rate and converting it into a digitalsignal, a motion detecting means 503 for detecting a motion vectorbetween frames, a DCT means 504 for performing discrete cosine transform(DCT) which is a method of bandwidth compression in which a digitalvideo signal is transformed into vertical and horizontal spatialfrequencies for data compression, an adaptive quantization means 505 forquantizing the transformed digital video signal, an inverse quantizationmeans 506, an inverse DCT (IDCT) means 507 for restoring an originaldigital video signal from the spatial frequency components, a framememory 508 for storing a reference image according to a motion vectorsent from the motion detecting means 503, a variable-length coding means509 for coding the quantized, digital video signal, a buffer memory 510,and a format encoder 511 for formatting a data structure of the coded adigital video signal. The above components from the A/D conversion means502 to format encoder 511 serve to perform image informationcompression.

A modulating means 512 is for modulating the formatted digital videosignal for the purpose of preventing intercode interference on anoptical disk. A laser modulating means 513 is for modulating a recordinglaser beam according to information sent from the modulating means 512.An optical disk 514 is for recording information by magneto-opticalrecording, phase change recording, or the like. An optical head 515 isfor recording information on the optical disk 514 according to therecording laser beam that has been modulated by the laser modulatingmeans 513. A feed motor 516 is for causing the optical head 515 to movein a radial direction of the optical disk 514. A disk motor 517 is forrotating the optical disk 514 at a given frequency. A servo circuit 518is for performing focus/tracking control of the optical head 515,control over the feed motor 516, and control over the disk motor 517. Asystem controller 519 is for producing control signals destined for theservo circuit 518, format encoder 511 and the like, and for controllingthe whole device. A playback amplifier 520 is for reproducing headerinformation of the image data recorded on the optical disk 514. A headeridentifying means 521 is for identifying a recording position on theoptical disk on the basis of reproduced header information. Referencenumeral 522 denotes a scene change detecting means.

FIG. 29 shows recording tracks shown to extend linearly, on which imageinformation blocks are recorded by the device of Embodiment D1. In thedrawing, reference numeral 523 denotes I-picture data of a GOP1 that isan image information block at a certain time instant. 524 denotes P- andB-picture data of the GOP1. 525 denotes I-picture data of a GOP2 that isan image information block temporally contiguous to the GOP1. 526denotes P- and B-picture data of the GOP2. 527 denotes I-picture data ofa GOP3 that is an image information block temporally contiguous to theGOP2. 528 denotes P- and B-picture data of the GOP3.

Reference numeral 529 denotes an address area defined in a headerappended to the start of the I-picture data 523 of the GOP1. Stored inthe address area 529 are the start position (hereinafter referred to asaddress information) of I-picture data of, for example, a GOP -1 that isan image information block temporally preceding the GOP1 and having ascene change detected, and the address information of the I-picture data527 of the GOP3 that is an image information block temporally succeedingthe GOP1 and having a scene change detected. 530 denotes an address areadefined in a header appended to the start of the I-picture data 527 ofthe GOP3. Stored in the address area 530 are the address information ofthe I-picture data 523 of the GOP1 that is an image information blocktemporally preceding the GOP 3 and having a scene change detected, andthe address information of the I-picture data of, for example, a GOP7that is an image information block temporally succeeding the GOP3 andhaving a scene change detected.

FIG. 30 is a schematic representation of the image information obtainedby sampling input original image information sampled by means of the A/Dconversion means 502 at a certain frame rate. In the drawing, referencenumerals 531 to 534 denote frames (screens) at time instants T0 to T3.

FIG. 31 shows the distribution of absolute values of differences inluminance signal level between adjoining frames obtained by sampling theoriginal images at the time instants T0 to T3 in FIG. 30. In thedrawing, L denotes a threshold used for scene change detection. When anabsolute value of a difference in luminance signal level betweenadjoining frames exceeds the L level, occurrence of a scene change isrecognized.

The operations of this embodiment will be described below. Referring toFIG. 28, an input video signal is sampled at a certain frame rate by theA/D conversion means 502. The amount of motion of the image is detectedin the form of a motion vector for each frame by the motion detectingmeans 503, and is transformed into vertical and horizontal spatialfrequencies by the DCT means 504, and subjected to adaptive quantizationby the adaptive quantization means 505.

Also in the present embodiment, information is recorded, in the units ofone image information block (equivalent to a GOP) composed of severalframes to several tens of frames. As described in conjunction with theprior art, each image information block contains a two-dimensionallycompressed image (I picture) that can be compressed by itself, andthree-dimensionally compressed images (P and B pictures) each of whichis compressed using a reference image, with the motion relative to atemporally preceding or succeeding image being represented by a motionvector.

As shown in FIG. 28, a reference image necessary for producing athree-dimensionally compressed image is formed by restoring image datafrom the adaptive quantization means 505, by means of the inversequantization means 506 and IDCT means 507, and then modifying therestored image data according to a motion vector provided by the motiondetecting means 503 in the frame memory 508.

Next, the compressed digital image data that has been subjected toadaptive quantization is variable-length coded according to themagnitude of the motion vector by means of the variable-length codingmeans 509, and then temporarily stored in the buffer memory 510.

The data structure of GOPs of the compressed digital image data thusstored in the buffer memory 510 are reformatted by the format encoder511 in response to an instructions from the system controller 519.Thereafter, a header and other information are appended to the imagedata. Resultant data is then supplied from the format encoder 511.

The thus formatted digital image information is modulated by themodulating means 512 in such a way that inter-code interference will notoccur on the optical disk 514. The resultant information is recorded onthe optical disk 514 by the optical head 515 via the laser modulatingmeans 513.

In this embodiment, a total sum, for each frame, of absolute values ofdifferences in the original image luminance signal level andcolor-difference signal level of each pixel between frames of the imagesampled by the A/D conversion means 502 is used for scene changedetection. Assuming that the distribution of absolute values ofdifferences in the luminance signal level between adjoining frames atthe time instants T0 to T3 in FIG. 30 is plotted as, for example, shownin FIG. 31, a scene change is found to have occurred at each of the timeinstants T1 and T3.

When information representing the frame at the time instant T1 or T3 atwhich the scene change is detected is compressed to form an I picture ofa GOP, the address information of the I picture is recorded at aposition preceding or succeeding the GOP and at the start (address area529, 530 in FIG. 29) of the I picture of the GOP at which the scenechange has been found. When information representing the frame at thetime instant T1 or T3 at which the scene change is detected iscompressed to form a P or B picture of a GOP, the address information ofthe I picture of the next GOP is recorded at a position preceding orsucceeding the GOP and at the start (address area 529, 530 in FIG. 29)of the I picture of the GOP at which the scene change has been found.This is because even if the address information were recorded in the Por B picture, preceding or succeeding I or P picture is required forreproducing the P or B picture, and the playback requires time.

During playback, I-picture data is consecutively reproduced on the basisof the information recorded in the address areas. This enables fastforward playback or retrieval, or fast reverse playback or retrieval inwhich only the pictures preceding and succeeding the scene changes areextracted. Consequently, fast playback or retrieval can be realizedefficiently in harmony with human visual characteristics.

An optical disk where MPEG-conformable compressed image information isrecorded on an optical disk at an average rate of 4 megabits per secondfor 135 minutes has image information areas of about four gigabytes longon one disk surface. If a sector size is 1024 bytes, the addressinformation for the image information areas can be represented by alength of three bytes. When address information indicating a position atwhich a scene change is detected is represented by four bytes, 256positions of scene changes can be recorded per sector. Assuming thatfast playback or retrieval is carried out at a 100-times speed, for thecase of the image signal of 30 frames per second, such a fat playback orretrieval can be achieved with registration of 2430 scene changes. Fastplayback or retrieval is achieved by sequential reproduction on thebasis of address information indicating registered positions of scenechanges.

Embodiment D2

Next, the Embodiment D2 will be described with reference to FIG. 32 andFIG. 33.

FIG. 32 shows the arrangement on recording tracks on the optical disk514. In the drawing, reference numerals SP1 to SP4 denote startpositions of four areas (blocks) into which each recording track isdivided equally.

FIG. 33 shows image information blocks illustrated to extend linearly,on the recording tracks shown in FIG. 32. Also in this embodiment, as inEmbodiment D1, a scene change is supposed to occur at each of the timeinstants T1 and T3. In the drawing, reference numeral 535 denotesI-picture data of a GOP1 that is an image information block at a certaintime instant. 536 denotes P- and B-picture data of the GOP 1. 537denotes I-picture data of a GOP2 that is an image information blocktemporally contiguous to the GOP1. 538 denotes P- and B-picture data ofthe GOP2. 539 denotes a P- and B-picture data of a GOP3 that is an imageinformation block temporally contiguous to the GOP2. 540 denotesI-picture data of the GOP3.

Reference numeral 541 denotes an address area provided in a header areaat the start of the I-picture data 535 of the GOP1. Stored in theaddress area 541 are the start position (address information) ofI-picture data of, for example, a GOP -1 that is an image informationblock temporally preceding the GOP1 and having a scene change detected,and the address information of the I-picture data 540 of the GOP3 thatis an image information block temporally succeeding the GOP1 and havinga scene change detected. 542 denotes an address area provided in aheader area at start of the I-picture data 540 of the GOP3. Stored inthe address area 542 are the start position (address information) of theI-picture data 535 of the GOP1 that is an image information blocktemporally preceding the GOP3 and having a scene change detected, andthe start position of I-picture data of, for example, a GOP7 that is animage information block temporally succeeding the GOP3 and having ascene change detected.

In Embodiment D1, the position of an I picture within each GOP is fixed.For this reason, the start position of an I picture within each GOP hasno correlation to the position on a recording track, along thecircumferential direction, of the track of an optical disk, i.e., to theangular position. Every time a jump is made to another track, afterI-picture data at a certain time instant is reproduced, in order toaccess the start position of I-picture data to be reproduced next, arandom optical disk rotation wait time waiting arises. It is thereforedifficult to achieve smooth reproduction of consecutive I-picture data.

In this embodiment, the position of an I picture within a GOP in which ascene change is detected can be varied. After data is allocated by theformat encoder 511 in such a way that the start positions of I picturesof GOPs will coincide with any of the positions SP1 to SP4 in FIG. 32,the data is recorded on the optical disk 514. Consequently, in thisembodiment, after the I picture 535 of the GOP1 at the position SP1 isreproduced, a track jump is made, after waiting for a given rotatingtime, to the start position SP3 of the I picture 540 of the GOP3 whichis read from the address information 541 beforehand. The I-picture data540 of the GOP3 can then be reproduced. Thus, smooth, consecutiveplayback of I-pictures taking account of the rotation wait time requiredfor track jumps can be achieved.

For the allocation of I pictures of GOPs in which scene changes havebeen detected, the picture data of GOPs is placed in memory at the timeof recording. Based on the length of the GOP, length of the I-picturedata, and the rotation wait time associated with the track jump, thestart position of the I picture is readily set to any appropriate one ofthe positions SP1 to SP4. In this embodiment, each GOP is assumed to beof a fixed rate. Alternatively, each GOP may be of a variable rate, andyet, in this alternative, the aforesaid procedure is applicable.Furthermore, in the above embodiment, the start positions of I picturesare set to any of four angular positions on an optical disk; positionsSP1 to SP4. Alternatively, any other number of positions may bespecified taking account of the length of the GOP containing data, thelength of the I-picture data, and the rotation wait time associated withthe track jump. This alternative has substantially the same advantage asthe above embodiment.

Embodiment D3

Next, Embodiment D3 will be described with reference to FIG. 34 and FIG.35.

FIG. 34 schematically shows images obtained by sampling the inputoriginal image information at a certain frame rate by means of the A/Dconversion means 502. In the drawing, reference numerals 543 to 553denote frames (screens) at time instants T0 to T10.

FIG. 35 shows the distribution of absolute values of differences inluminance signal level between with respect to the adjoining frame,obtained by sampling at the time instants T0 to T10 in FIG. 34. In FIG.35, L0 denotes a first threshold used for scene change detection. L1denotes a second threshold used for scene change detection. L2 denotes athird threshold used for scene change detection. When an absolute valueof a difference in luminance signal level exceeds the value L0, L1, orL2, occurrence of a scene change is recognized.

In this embodiment, as in Embodiment D1 described above, when I-, P-,and B-picture data having been image compressed from the original imagesis constructed, luminance and color-difference signals representing theoriginal image for one frame are used to detect a scene change. UnlikeEmbodiment D1, this embodiment defines a plurality of thresholds forscene change detection. Scene change detection is carried out in usingeach of the thresholds. Assuming that the distribution of absolutevalues of differences in luminance signal level between adjoining framesat the time instants T0 to T10 is plotted as shown in FIG. 34, when thethreshold L0 are used, scene changes are found to have occurred at thetime instants T1, T2, T4, T6, and T8. When the threshold L1 are used,scene changes are found to have occurred at the time instants T2 and T8.When the threshold L2 is used, scene change are found to have occurredat the time instant T8.

In this embodiment, an address area is provided at the start of the Ipicture of the GOP for which a scene change has been detected, theaddress area being divided into sections for the respective thresholds.

By adopting the above configuration, fast playback or retrieval can beachieved at various multiple speeds using the different thresholds. Byselecting the threshold, fast playback or retrieval can be achieved withevery occurrence of a finer scene change or a rougher scene change.Furthermore, a higher speed can be selected freely for fast playback orretrieval.

Specifically, a higher threshold is used for a higher playback orretrieval speed, so that playback or retrieval is conducted using onlythe I pictures for which a rougher scene change has found to haveoccurred. By contrast, playback or retrieval at a lower speed isconducted using the I pictures for which a finer scene change (detectedwith the threshold L0) has found to have occurred.

Also in this embodiment, as in Embodiment D2, it may be so arranged thatthe start position of I-picture data of a GOP in which a scene change isdetected may be set to any of the angular positions on each recordingtrack on an optical disk; SP1 to SP4. In this case, this embodiment hasthe same advantage as Embodiment D2.

In Embodiments D1 to D3 described above, an address area forfacilitating fast playback or retrieval is provided in a header part atthe start of an I picture of a GOP for which a scene change is detected.Alternatively, as shown in FIG. 36, address information may becollectively recorded in a specific recording area defined on an opticaldisk 514. FIG. 36 shows an optical disk on which image informationaccording to the present embodiment is recorded. In the drawing,reference numeral 554 denotes an image information area in which asuccession of consecutive image information blocks each composed of I-,P-, and B-picture data are recorded. 555 denotes an address area definedalong the innermost or outermost circumference of an optical disk anddesigned to store address information of I pictures of GOPs containingscene changes.

The scene changes detected with a plurality of thresholds as in thisembodiment, in the address area 555 can be recorded in a manner shown inFIG. 37. In the drawing, reference numerals 556a, 556b, and 556c denotevalues of thresholds of detection levels L0, L1, and L2 used for scenechange detection. 557a, 557b, and 557c denote address informationindicating the start positions on an optical disk of I pictures of GOPsfor which scene changes have been detected with the respectivethresholds.

Address information of the I pictures of GOPs for which scene changeshave been detected are stored in advance in a memory for each of thethresholds. The information is then recorded in the address area 555.Assuming that AD0 to AD10 are I picture address information on theoptical disk corresponding to the time-base information for the timeinstants T0 to T10, the data recorded in the address area 555 will besomething like (L0, AD1), (L1, AD2), (L0, AD4), and (L2, AD8), or like(556a, 557a), (556a, 557b), and (556c, 557c) in FIG. 37.

For reproduction, the information in the address area 555 is read outbeforehand. Only the I-picture data of GOPs containing scene changesassociated with the threshold selected by a viewer is consecutivelyreproduced.

Embodiment D4

Embodiment D4 will next be described with reference to FIG. 38 and FIG.39.

FIG. 38 shows recording tracks, illustrated to extend linearly, on whichimage information blocks are recorded according to this embodiment. Inthe drawing, reference numeral 558 denotes I-picture data of a GOP1 thatis an image information block at a certain time instant. 559 denotes P-and B-picture data of the GOP1. 560 denotes P-and B-picture data of aGOP2 that is an image information block temporally contiguous to theGOP1. 561 denotes I-picture data of the GOP2. 562 denotes I-picture dataof a GOP3 that is an image information block temporally contiguous tothe GOP2. 563 denotes P- and B-picture data of the GOP3.

Reference numeral 564 denotes an address area provided in a header partat the start of the I-picture data 558 of the GOP1. Stored in theaddress area 564 are address information of I-picture data of a GOP 0that is an image information block immediately preceding the GOP1, andaddress information of the I-picture data 561 of the GOP2 that is animage information block immediately succeeding the GOP1. 565 denotes anaddress area defined in a header part at the start of the I-picture data561 of the GOP2. Stored in the address area 565 are address informationof the I-picture data 558 of the GOP1 that is an image information blockimmediately preceding the GOP2, and address information of the I-picturedata 562 of the GOP3 that is an image information block immediatelysucceeding the GOP2. 566 denotes an address area provided in a headerpart at the start of the I-picture data 562 of the GOP3. Stored in theaddress area 566 are address information of the I-picture data 561 ofthe GOP2 that is an image information block immediately preceding theGOP3, and address information of the I-picture data of a GOP4 that is animage information block immediately succeeding the GOP3.

In this embodiment, each GOP is structured as shown in FIG. 38. Addressinformation of the I pictures of GOPs for which scene changes have beendetected is recorded in the address area 555 (See FIG. 36) on an opticaldisk, as described in conjunction with FIG. 36. This allows a viewer tofreely select the mode of fast playback or retrieval using scene changesor the mode of playback or retrieval using adjoining GOPs. For unwantedparts, fast playback retrieval may be executed in scene change-dependentmode. For wanted parts, fast playback or retrieval may be executed inadjoining GOP-based mode in which adjoining GOPs are reproduced orretrieved consecutively. Thus, fast playback or retrieval can beachieved at a suitable speed.

FIG. 39 is a flowchart illustrating the operations of an optical diskdevice for performing the aforesaid fast playback or retrieval. First,when fast playback or retrieval is started, a viewer selects aplayback/retrieval mode from between the scene change-dependent mode andadjoining GOP-based mode. When the scene change-dependentplayback/retrieval is selected, a playback/retrieval level is designatedby selecting any of the thresholds L0 to L2 in FIG. 35. Based on thedesignated level, information representing the positions of desiredscene changes is read from the address area 555. Fast playback/retrievalis executed according to the position information. By contrast, when theadjoining GOP-based mode in which I pictures of adjoining GOPs areconsecutively reproduced or retrieved is selected, after I-picture dataof a certain GOP is reproduced, a track jump is made in order to accessthe start position of I-picture data of an adjoining GOP indicated bythe address information recorded at the start of the I-picture datahaving been reproduced. The I-picture data accessed is then reproduced.This operation is repeated until the viewer instructs termination offast playback/retrieval.

According to the device for and method of optical diskrecording/playback of Embodiments D1 to D4, fast playback or retrievalcan be performed in harmony with human visual characteristics,especially, a characteristics that human eyes are sensitive to scenechanges. A viewer can therefore retrieve his/her wanted images quickly.

In addition, according to the present embodiment, the start positions oftwo-dimensionally compressed images used for fast playback or retrievalare always aligned at predetermined angular positions on an opticaldisk, i.e., along radially extending straight lines. This makes itpossible to perform reproduction taking account of the rotation waittime associated with the track jump of the optical pickup during fastplayback or retrieval. Consequently, smooth, consecutive playback oftwo-dimensionally compressed images can be achieved with ease.

Furthermore, according to the present embodiment, a plurality ofthresholds are used for detecting scene changes. This makes it possibleto use a plurality of different speeds for fast playback or retrievaland to speed up the fast playback or retrieval. According to theaforesaid method, speedup is carried out in harmony with human visualcharacteristics. A viewer can therefore identify wanted imagesrelatively easily from among images even at the increased playback orretrieval speed.

In the above embodiments, a viewer can select either fastplayback/retrieval dependent on scene changes or fast playback/retrievalbased on adjoining GOPs according to his/her need. For wanted parts,adjoining GOP-based fast playback/retrieval may be selected to performretrieval at a relatively low speed with excellent precision. Forunwanted parts, scene change-dependent fast playback/retrieval may beselected to perform retrieval at a very high speed, which is a speedharmonious with human visual characteristics, with minimum requiredprecision.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A video disk recording and playback method forrecording and playing back a video signal, comprising the stepsof:converting a digital video signal composed of a succession of videosignals of a plurality of frames into coded data including an I pictureencoded within a frame, a P picture interframe coded by forward motioncompensation with reference to said I picture and/or another P picture,and a B picture interframe coded by motion compensation in bothdirections with reference to said I and/or P pictures temporallypreceding and succeeding said B picture; recording the coded data on avideo disc; manipulating a switch to select an image represented by thecoded data wherein a user manipulates the switch to select the image;constructing an image information table containing a start address ofcoded data representing the selected image and the start address ofheader data, said header data containing information required forreproducing the selected image including at least a group of picturesheader corresponding to the selected image.
 2. A video disc encoded bythe video disc recording and playback method recited in claim
 1. 3. Thevideo disk recording and playback method as set forth in claim 1,further comprising the step of:recording the image information table onthe video disc.
 4. The video disk recording and playback method as setforth in claim 1, further comprising the step of:accessing the imageinformation table on the video disc to reproduce the selected image. 5.A video disk recording/playback device comprising:a converter convertinga digital video signal into high-efficiency coded data including an Ipicture encoded within a frame, a P picture interframe coded by forwardmotion compensation with reference to said I picture and/or another Ppicture, and a B picture interframe coded by motion compensation in bothdirections with reference to said I and/or P pictures temporallypreceding and succeeding the B picture; a recorder recording thehigh-efficiency coded data on a video disk; a decoder restoringhigh-efficiency coded data recorded on the video disk to generate anoutput image; a switch manipulated by a user to select images coded byan I picture, a P picture and/or a B picture; recording means forrecording in an image information table all of the start addresses ofcoded data representing the selected images and the start addresses ofeach group of pictures header containing information required forreproducing corresponding selected images.
 6. The video diskrecording/playback device as set forth in claim 5, wherein saidrecording means records the image information table on said video disk.7. The video disk recording/playback device as set forth in claim 5,wherein said switch may be manipulated by the user to select an inputimage as the selected image during recording of said input images on thevideo disk by said recording means.
 8. The video disk recording/playbackdevice as set forth in claim 5, said switch being manipulated by theuser to select one of the output images as the selected image duringrestoration of coded data recorded on the video disk and output of saidoutput images by said decoder.
 9. The video disk recording/playbackdevice as set forth in claim 5, further comprising means for low-passfiltering the selected images that have been decoded, means forsub-sampling images that have been filtered, means for storing thesub-sampled images, and means for displaying a single or a plurality ofselected sub-sampled images recorded on the video disk as small screensthat are N (N≧1) fractions of one screen.
 10. The video diskrecording/playback device as set forth in claim 5, wherein saidrecording means also stores an ID signal for identifying the video disk.11. The video disk recording/playback device as set forth in claim 10,further comprising means for recording the ID signal in a specific partof the video disk.
 12. The video disk recording/playback device as setforth in claim 10, said switch being manipulated by the user to selectan image being recorded on the video disk, as the selected image. 13.The video disk recording/playback device as set forth in claim 10, saidswitch being manipulated by the user to select an image which is beingoutput, by restoration of its coded recorded on the video disk, as theselected image.
 14. The video disk recording/playback device as setforth in claim 10, further comprising:means for low-pass filtering theselected images having been decoded; means for sub-sampling the filteredimages; and means for storing the sub-sampled images and displaying themas reduced screens of 1/N of a full screen.
 15. The video diskrecording/playback device as set forth in claim 5, furthercomprising:means for accessing the image information table, and meansfor reproducing the selected image according to the image informationtable accessed by said accessing means.
 16. A video disc recording andplayback method for recording a group of pictures on a video disc,comprising the steps of:encoding a group of pictures into an intra-frameencoded I picture; an inter-frame encoded, forward motion compensated Ppicture and an inter-frame encoded, forward and backward motioncompensated B picture; constructing a group of pictures headercontaining decoding information for decoding the group of pictures;designating an image within the encoded group of pictures wherein a userdesignates the image; recording the encoded group of pictures and thegroup of pictures header on the video disc; constructing an imageinformation table for the designated image including a start address ofthe designated image and a start address of the group of picturesheader; storing the image information table; accessing the imageinformation table to retrieve the start address of the designated imageand the start address of the group of pictures header; retrieving thedecoding information in the group of pictures header by using the startaddress of the group of pictures header retrieved in said accessingstep; decoding the designated image by starting with the I picture andprogressing to the designated image according to the decodinginformation in the group of pictures header; and outputting the decoded,designated image.
 17. The video disc recording and playback method ofclaim 16, said storing step further including storing the imageinformation table on the video disc.
 18. The video disc recording andplayback method of claim 16, further comprising the steps of:designatinga plurality of images; said constructing step constructing an imageinformation table for the designated images including a start addressfor each of the designated images and a start address of the group ofpictures header corresponding to each of the designated images; low-passfiltering the designated, decoded images; sub-sampling the filteredimages; storing the sub-sampled images; displaying the stored images assmall screens that are N (N≧1) fractions of one screen.
 19. The videodisc recording and playback method of claim 16, further comprising thestep of:recording an ID signal on the video disc to identify the videodisc.
 20. The video disc recording and playback method of claim 19, saidrecording an ID signal further including recording the ID signal on aspecific region of the video disc.
 21. The video disc recording andplayback method of claim 16, said outputting step further including thesubstep of displaying the decoded selected image on a display.
 22. Avideo disc encoded by the video disc recording and playback methodrecited in claim
 16. 23. The video disc recording and playback method ofclaim 16, further comprising the steps of:designating a plurality ofimages; said constructing step constructing an image information tablefor the designated images including a start address for each of thedesignated images and a start address of the group of pictures headercorresponding to each of the designated images.
 24. The video diskrecord and playback method of claim 16, said designating stepdesignating an inter-frame encoded, forward motion compensated Ppicture.
 25. The video disk recording and playback method of claim 16,said designating step designating an inter-frame encoded, forward andbackward motion compensated B picture.